Radunz Dissertation - OhioLINK ETD

5 downloads 0 Views 1MB Size Report
Tara, Martin, Rachel, and Jill. To my good friend, Amber ...... to reduce the proportion of slow-twitch muscle fibers in offspring in sheep (Costello et al., 2008).
EFFECTS OF PREPARTUM DAM ENERGY SOURCE ON PROGENY GROWTH, GLUCOSE TOLERANCE, AND CARCASS COMPOSITION IN BEEF AND SHEEP

DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By Amy E. Radunz, M. S. Graduate Program in Animal Science The Ohio State University 2009

Dissertation Committee Dr. Steven C. Loerch, Co-advisor Dr. Henry N. Zerby, Co-advisor Dr. Francis L. Fluharty Dr. Michael L. Day

Copyright by Amy E. Radunz 2009

ABSTRACT A series of experiments were conducted in cattle and sheep to investigate the effects of prepartum dietary energy source during gestation on pre- and postpartum dam performance as well as on progeny growth, insulin sensitivity, and carcass composition. The three dietary energy sources used for the experiments were hay or haylage (fiber, HAY); corn (starch, CORN); or dried distiller grains (fiber plus fat, DDGS) and diets were fed to dams at isoenergetic intakes during gestation. In the first experiment beef cows were used to determine the effects of late gestation dietary energy source on fetal growth and prepartum maternal hormone and blood metabolites. Cows fed HAY and CORN achieved the experimental objective of having similar body weight and body condition score change during late gestation, however, cows fed DDGS had greater body weight gain. This suggests DDGS may have a greater energy value than expected based on published reviews when limit-fed during gestation to beef cows. Calves from cows fed CORN and DDGS had heavier birth weights than calves from cows fed HAY.

Differences in plasma metabolites may

indicate differences in maternal metabolism in late gestation due to dietary energy source, which may affect partitioning of nutrients between maternal and fetal tissues. Progeny from the first experiment were weaned, and then fed a common finishing diet until the calves reached a common fat thickness.

These progeny were then

slaughtered. Differences in birth weight were still evident upon entry into the feedlot, as body weights were heavier for calves from cows fed CORN and DDGS than from those

ii

fed HAY. In contrast to arrival at the feedlot, carcass weights were lighter for calves from cows fed DDGS than from those fed CORN or HAY. Growth rate was not different among treatments from birth to slaughter, but calves from dams fed CORN were slaughtered at a younger age than calves from cows fed HAY or DDGS. Measures of carcass yield were not affected by treatment, whereas intramuscular fat (a component of USDA quality grade) was greater in calves from dams fed DDGS or HAY than from those fed CORN. In addition, initial insulin secretion in response to a glucose tolerance test was greater in calves from dams fed HAY than calves from dams fed CORN or DDGS and was associated with greater intramuscular fat content per unit of fat thickness. In the second experiment, mature ewes were fed dietary treatments in mid- to lategestation to determine effects on ewe prepartum metabolic energy status, postnatal progeny performance, glucose tolerance and carcass composition. During mid-gestation ewe body weight gain and body condition score were similar among treatments and met the experimental objective, whereas during late gestation body weight gain and body condition score were less at parturition in ewes fed HAY than those fed CORN or DDGS. Similar to experiment one, lamb birth weights tended to be greater in lambs from ewes fed CORN and DDGS than in lambs from ewes fed HAY. Greater maternal glucose concentrations were observed in ewes fed CORN, whereas greater maternal insulin and BUN concentrations were observed in ewes fed DDGS. Increased glucose and amino acid supply, as indicated by maternal metabolic status, could explain the increase in birth weight in lambs from ewes fed DDGS and CORN compared with that of lambs from ewes fed HAY.

iii

Overall growth rate from birth to slaughter was not different among treatments. Lambs from ewes fed DDGS vs. lambs from ewes fed CORN or HAY tended to have a greater initial insulin secretion due to glucose infusion in the glucose tolerance test. No difference was detected in HCW, fat thickness, proportion of seam fat, or intramuscular fat content among treatments. However, lambs from ewes fed DDGS vs. lambs from ewes fed CORN or HAY had a greater proportion of internal fat, less muscle, and lower calculated boneless trimmed retail cut percentage. The first experiment was repeated, because isoenergetic intakes were not achieved in the first experiment, and may have confounded responses observed. Cow body weight gain was similar among treatments during late gestation, thus, this experimental objective was met. Cows fed HAY vs. cows fed CORN or DDGS had greater non-esterified fatty acids, lower blood urea nitrogen, and lower insulin concentrations postfeeding, as well as lower progeny birth weights. At 93 days of age, progeny’s fed and fasted glucose and insulin concentrations were measured. Fasting glucose concentrations were greatest to least for calves from cows fed CORN, HAY, and DDGS, respectively, whereas fed glucose and insulin, and fasted insulin concentrations, were similar among treatments. In all three experiments, prepartum energy source did not adversely affect postpartum cow or ewe performance. Together these results suggest prepartum energy sources, which may increase maternal glucose and amino acid supply to the fetus, impact fetal growth and alter postnatal insulin sensitivity and adipose tissue development. These alterations in fetal development have long-term effects on carcass composition.

iv

Dedication To my mom and sisters In memory of my father Charles K. Radunz

v

ACKNOWLEDGEMENTS “The glory of friendship is not the outstretched hand, nor the kindly smile, nor the joy of companionship; it is the spiritual inspiration that comes to one when they discover that someone else believes in them and is willing to trust them.”~Ralph Waldo Emerson I have been fortunate to have several individuals encourage and believe in me even when I did not believe myself. To Drs. Steve Loerch, Henry Zerby and Francis Fluharty for having confidence in my abilities, providing employment, offering advice, bestowing your friendship, and teaching me lessons about science as well as life. I would like to thank Dr. Mike Day for his assistance in various aspects of my project and for serving on my committee. I greatly appreciate Dr. Ivanette Susin’s assistance, input, and friendship. I also need to extend my appreciation to several people who were instrumental to my data collection and sanity; Marty, Gregg, Wayne, Chris, Jim, Doug, Marcy, Roger, Rusty, Gary, and Pat. Furthermore, I would like to thank my fellow graduate students who have provided fellowship, intellectual stimulation, and support; Alejandro, Allen, Megan, Tara, Martin, Rachel, and Jill.

To my good friend, Amber Moffett, thanks for always

being willing to listen and open the door to your home. Final but by no means least, to my parents for their love and support as well as dedication to their faith, values, modesty, and hard-work ethic that have been an inspiration to me.

vi

VITA November 24, 1975

Born – Hutchinson, MN

May 1998

B.S., Animal Science, Department of Animal Science, North Dakota State University, Fargo, ND

August 1999- October 2001

Graduate Research Assistant, Department of Animal Science, North Dakota State University, Fargo, ND

December 2001

M.S., Animal Sciences (Ruminant Nutrition), Department of Animal Science, North Dakota State University, Fargo, ND

October 2001- September 2002

Beef Extension Associate, Department of Animal Science, The Ohio State University, Columbus, OH

September 2002- December 2004

Scientific Instructor Technician Supervisor, Animal Sciences Department, Washington State University, Pullman, WA

January 2005- December 2008

Program Specialist, Department of Animal Science, The Ohio State University, Columbus, OH

January 2009- Present

Graduate Research Associate, Department of Animal Sciences, The Ohio State University, Columbus, OH

PUBLICATIONS Radunz, A. E., L. A. Wickersham, S. C. Loerch, F. L. Fluharty, C. K. Reynolds, and H. N. Zerby. 2009. Effects of dietary polyunsaturated fatty acid supplementation on fatty acid composition in muscle and subcutaneous adipose tissue of lambs. J. Anim. Sci. doi: jas.2009-2059v1-20092059. Radunz, A. E., S. C. Loerch, G. D. Lowe, F. L. Fluharty, and H. N. Zerby. 2009. Effect of Wagyu- versus Angus-sired calves on feedlot performance, carcass characteristics, and tenderness. J. Anim. Sci. 87: 2971-2976.

vii

Radunz, A. E., H. N. Zerby, J. F. Grimes, G.D. Lowe, and F. L. Fluharty. 2007. Effect of weaning and post-weaning management of beef steers on carcass characteristics and tenderness. J. Anim. Sci. 85 (Supp 1). Radunz, A. E., P. S. Kuber, H. N. Zerby, S. J. Moeller, M. D. Vieson, G. R. Dunlap, A. C. Naber, J. L. Bard, K. M. Brueggemeier, and B.L. Gwartney. 2006. Effects of moisture enhancement on tenderness, retail color, and sensory characteristics of beef triceps brachii. J. Anim. Sci. 84 (Supp 2). Kuber, P. S., A. E. Radunz, M. D. Vieson, H. N. Zerby, S. J. Moeller, J. L Bard, A. C. Naber, K. M. Brueggemeier, G. R. Dunlap, and B. L. Gwartney. 2006. Effect of moisture enhancement on sensory attributes, tenderness and retail color of beef steaks from the vastus lateralis. J. Anim. Sci. 84 (Supp 2). Kuber, P. S., A. E. Radunz, M. D. Vieson, H. N. Zerby, S. J. Moeller, J. L Bard, A. C. Naber, K. M Brueggemeier, G. R. Dunlap, and B. L. Gwartney. 2006. Effect of moisture enhancement on sensory attributes, tenderness, and retail color of beef steaks from the rectus femoris. J. Anim. Sci. 84 (Supp 2). Vieson, M. D., P. S. Kuber, H. N. Zerby, A. E. Radunz, S. J. Moeller, J. L. Bard, A. C. Naber, K. M Brueggemeier, G. R. Dunlap, and B. L. Gwartney. 2006. Effect of moisture enhancement on sensory attributes, tenderness and retail color of beef steaks from the gluteus medius. J. Anim. Sci. 84 (Supp 2). Baumann T. A., A. E. Radunz, G. P. Lardy, V. L. Anderson, J. A. Caton, and M. L. Bauer. 2004. Effects of tempering and a yeast-enzyme mixture on intake, ruminal fermentation, in situ disappearance, performance and carcass traits in steers fed barley-based diets. Prof. Anim. Sci. 20:178. Radunz, A. E., G. P. Lardy, M. L. Bauer, M. J. Marchello, E. R. Loe, and P. T. Berg. 2003. Influence of steam-peeled potato-processing waste inclusion level in beef finishing diets: Effects on digestion, feedlot performance, and meat quality. J. Anim. Sci. 81: 2675-2685. Encinias, A. M., H. B. Encinias, A. E. Radunz, M. L. Bauer, R. B. Danielson, G. P. Lardy, and C. S. Park. 2000. Stair-step compensatory growth regimen in gestating beef heifers. J. Anim. Sci. 78 (Supp 1): 258. Scheaffer, A. N., A. E. Radunz, A. M. Encinias, M. L. Bauer, G. P. Lardy, and J. S. Caton. 2000. Influence of field pea supplementation on intake and performance of gestating beef cows fed grass hay diets. Can J. Anim. 80:782.

FIELDS OF STUDY Major Field: Animal Sciences Emphasis: Meat Science, Ruminant Nutrition

viii

TABLE OF CONTENTS

Abstract……………………………………………………………………………… Dedication………………………………………………………………………….... Acknowledgements………………………………………………………...………... Vita ...……………………………………………………...………………................ List of Tables………………………………………………………...………………. List of Figures………………………………………………………...……………...

Page ii v vi vii xi xiii

Chapters 1. Literature Review………………………………………...… …………...………. Introduction………………………………………...………………...………… Effects of maternal nutrition on dam performance…………………………….. Effects of maternal nutrition on offspring………………………………………

1 1 3 12

2. Effects of prepartum dietary energy source on pre- and postpartum cow performance………………………………………………………………............. Abstract…………………………………………………………………………. Introduction……………………………………………………………………... Materials and Methods………………………………………………………….. Results and Discussion…………………………………………………………. Literature Review……………………………………………………………….

31 31 32 34 39 49

3. Effects of prepartum dam dietary energy source on postnatal growth, glucose tolerance, and carcass composition of progeny in beef cattle……………….…... Abstract…………………………………………………………………………. Introduction……………………………………………………………………... Materials and Methods………………………………………………………….. Results and Discussion…………………………………………………………. Literature Review……………………………………………………………….

66 66 67 68 75 86

4. Effects of prepartum dietary energy source on pre- and postpartum performance of ewes and preweaning performance of lamb progeny………………………… Abstract………………………………………………………………………... Introduction………………………………………………………………......... Materials and Methods………………………………………………………… Results and Discussion………………………………………………………… Literature Review………………………………………………………………

103 103 104 106 110 119

ix

5. Effects of prepartum ewe dietary energy source on postweaning growth, glucose tolerance, and carcass composition of lamb progeny ……………….... Abstract……………………………………………..…………………………. Introduction………………………………………...…………………….......... Materials and Methods………………………………………..………………. Results and Discussion………………………………………………………… Literature Review………………………………………………………………

135 135 136 137 143 150

6. Effects of cow prepartum dietary energy source on prepartum cow plasma insulin and metabolites and progeny preweaning performance ………………... Abstract……………………………………………..…………………………. Introduction………………………………………...…………………….......... Materials and Methods………………………………………..………………. Results and Discussion………………………………………………………… Literature Review………………………………………………………………

164 164 165 167 171 179

7. Conclusions………………………………………………………………………

193

Bibliography…………………………………………………………………………

200

x

LIST OF TABLES Page 2.1. Reasons for cows being removed from the trial………………………………..

55

2.2. Late gestation diets and nutrient composition……………..…………………...

56

2.3. Nutrient intake and daily feed cost during gestation……………………………

57

2.4. Effects of prepartum energy source on gestation cow performance……………

58

2.5. Effects of prepartum energy source on postpartum cow performance and milk production……………………………………………………………………...

59

2.6. Effects of prepartum energy source on reproductive performance……………..

60

3.1. Progeny backgrounding supplement and finishing diet composition…………..

91

3.2. Effects of prepartum dam dietary energy source on progeny measurements at parturition………………………………………………………………………

92

3.3. Effects of prepartum dam dietary energy source on progeny health……………

93

3.4. Effects of prepartum dam dietary energy source on progeny at weaning............

94

3.5. Effects of prepartum dam dietary energy source on progeny glucose tolerance..

95

3.6. Effects of prepartum dam dietary energy source on progeny feedlot performance ………………………...…………………………………………

96

3.7. Effects of prepartum dam dietary energy source on progeny carcass composition and distribution of yield and quality grade.……………………..

97

3.8. Effects of prepartum dam dietary energy source on costs and returns of progeny from birth to slaughter……………………………………………….

98

4.1. Mid-gestation (d 80 to 115) diets provided to ewes……………………………

123

4.2. Nutrient intake during mid-gestation (d 80 to 115)……………………………

124

4.3. Reasons for ewes being removed from the trial………………………………..

125

xi

4.4. Effects of prepartum dam dietary energy source on twin progeny organ weights and leg composition sacrificed at birth ……………………………..

126

4.5. Effects of prepartum energy source on 28 d milk production………………….

127

4.6. Effects prepartum dam dietary energy source on progeny preweaning performance…………………………………………………………………...

128

5.1. Progeny finishing diet composition……………………………………………

154

5.2. Effects of prepartum dam dietary energy source on progeny feedlot performance…………………………………………………………………...

155

5.3. Effects of prepartum dam dietary energy source on progeny glucose tolerance measurements…………………………………………………………………

156

5.4. Effects of prepartum dam dietary energy source on progeny carcass characteristics…………………………………………………………………

157

5.5. Effects of prepartum dam dietary energy source on progeny wholesale cuts…

158

5.6. Effects of prepartum dam dietary energy source on progeny muscle weights and percentage of wholesale cuts……………………………………………..

159

5.7. Effects of prepartum dam dietary energy source on progeny fat weights and percentage of wholesale cuts………………………………………………….

160

5.8. Effects of prepartum dam dietary energy source on progeny on bone weights and percentage of wholesale cuts……………………………………………..

161

6.1. Reasons for cows being removed from the trial……………………………….

183

6.2. Late gestation diets and nutrient composition………………………………….

184

6.3. Nutrient intake and daily feed costs during gestation………………………….

185

6.4. Effects of prepartum dietary energy source on gestation cow performance……………………………………………………………….….

186

6.5. Effects of prepartum dietary energy source on cow postpartum performance, milk production, and milk composition.…………………………………..….

187

6.6. Effects of prepartum dietary energy source on progeny preweaning measurements………………………………………………………………....

188

xii

LIST OF FIGURES

Page 1.1. Sheep conceptus development in gestation and periods of specific organ development that can be influenced by maternal nutrition……………………

13

2.1. Plasma glucose concentration before and after feeding at 210 d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation…………………..

61

2.2. Plasma insulin concentration before and after feeding at 210 d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation…………………..

62

2.3. Plasma NEFA concentration before and after feeding at 210 d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………

63

2.4. Plasma BUN concentration before and after feeding at 210 d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………

64

2.5. Plasma progesterone concentration during late gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………….…..

65

3.1. Plasma glucose concentration before and after glucose bolus infusion after 50 d on finishing diet in calves from dams fed ad libitum hay (HAY; ), limitfed corn (CORN; ), or limit-fed dried distiller grains (DDGS; ) in late gestation………………………………………………………………………..

99

3.2. Plasma insulin concentration before and after glucose bolus infusion after 50 d on finishing diet in calves from dams fed ad libitum hay (HAY; ), limitfed corn (CORN; ), or limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………..

100

3.3. Plasma glucose-dependent insulinotropic polypeptide concentration before and after glucose bolus infusion after 50 d on finishing diet in calves from dams fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), or limit-fed dried distiller grains (DDGS; ) in late gestation…………………………..

101

xiii

3.4. Plasma glucose-like peptide-I concentration before and after glucose bolus infusion after 50 d on finishing diet in calves from dams fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), or limit-fed dried distiller grains (DDGS; ) in late gestation………………………………………………..

102

4.1. Pre- and postpartum body weight in ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

129

4.2. Pre- and postpartum body condition score in ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………….

130

4.3. Plasma glucose concentration before and after feeding at approximately 80 (A) and 122 (B) d of gestation from ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

131

4.4. Plasma insulin concentration before and after feeding at approximately 80 (A) and 122 (B) d of gestation from ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

132

4.5. Plasma BUN concentration before and after feeding at approximately 80 (A) and 122 (B) d of gestation from ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

133

4.6. Plasma NEFA concentration before and after feeding at approximately 80 (A) and 122 (B) d of gestation from ewes fed haylage (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

134

5.1. Plasma glucose concentration before and after glucose bolus infusion after 50 d on finishing diet in lambs from dams fed ad libitum hay (HAY; ), limitfed corn (CORN; ), or limit-fed dried distiller grains (DDGS;) in late gestation………………………………………………………………………

162

5.2. Plasma insulin concentration before and after glucose bolus infusion after 50 d on finishing diet in lambs from dams fed ad libitum hay (HAY; ), limitfed corn (CORN; ), or limit-fed dried distiller grains (DDGS;) in late gestation………………………………………………………………………

163

xiv

6.1. Plasma glucose concentration before and after feeding at 189 (A) and 235 (B) d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation……………………………………………………………………….

189

6.2. Plasma insulin concentration before and after feeding at 189 (A) and 235 (B) d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation………...

190

6.3. Plasma NEFA concentration before and after feeding at 189 (A) and 235 (B) d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation………...

191

6.4. Plasma BUN concentration before and after feeding at 189 (A) and 235 (B) d of gestation from cows fed ad libitum hay (HAY; ), limit-fed corn (CORN; ), and limit-fed dried distiller grains (DDGS; ) in late gestation………...

192

xv

CHAPTER 1 LITERATURE REVIEW

Introduction Beef cattle production in the United States is facing many challenges, from maintaining economic viability during times of low profitability, to not meeting consumer demands for high quality product. More recently, increased production of ethanol has reduced the availability of corn for livestock feed, potentially creating an environment where increased production costs may negate profitable beef production. Concurrently, growth of coordinated industry segments, retained ownership, value-based marketing, and source-verified programs, all emphasize optimizing management practices and nutrition programs throughout the production system to minimize negative impacts on the value of the carcass. While these two challenges may appear antagonistic, they may provide incentive for increased cooperation among segments of the industry and enhance viability. Consequently, long-term effects of nutrition and management practices on economically important production and carcass traits will be critical information for the beef industry. Recently, cost of production has risen dramatically, mainly due to increased feed and energy costs. One of the major determinants of net income in a cow/calf enterprise is cow production costs, of which the largest portion is feed (Story et al., 2000).

1

Minimizing feed costs without sacrificing nutrient intake is crucial, since nutritional status of gestating cows is positively correlated with calf health and weaning weight (Corah et al, 1975; Stalker et al., 2006). An alternative to traditional forage-based diets, limit-fed corn, can reduce daily feed costs during gestation (Loerch, 1996) without being detrimental to cow performance or calf postnatal growth. However, corn-based diets are limited in protein and require supplementation with expensive protein sources. With increased availability of ethanol co-products, dried distillers grains (DDGS) have become more competitively priced with other protein and energy sources, and could be a viable option at higher inclusion levels in gestation diets. However, little information has been published on the effects of DDGS in limit-fed prepartum diets on cow performance. The effects of nutrition during pregnancy on subsequent long-term growth and meat quality of the offspring will become increasingly important as segments of the beef industry integrate. Evidence suggests that maternal nutrient intake can alter subsequent skeletal muscle development, body composition, and energy metabolism in early postnatal life of offspring (Wu et al., 2006). Intrauterine growth retardation (IUGR), defined as impaired growth and development of the fetus or its organs during pregnancy, is a significant problem in livestock production as well as in human health. Low birth weight is associated with high neonatal morbidity and mortality, decreased postnatal growth, increased adiposity, and less muscle mass (Greenwood et al., 2002). Excessive and restricted nutrition during gestation in ewes have both been associated with intrauterine growth retardation (Wallace et al. 2004). Additionally, individual nutrients in maternal diets, such as protein, have been associated with long-term postnatal growth and carcass characteristics in steer progeny, and fertility in heifer progeny in beef cattle

2

(Martin et al., 2006; Stalker et al., 2007; Larson et al., 2009). Energy source may also alter fetal development. Studies investigating starch- vs. fiber- based gestation diets may alter prenatal fetal growth as evidenced by greater calf birth weights (Loerch, 1996). In a review, Wu et al. (2006) presented compelling evidence suggesting fetal intrauterine environments may have lifelong consequences by altering expression of the fetal genes during gestation. Fetal programming as described above has far reaching implications for food animal production especially if these effects impact muscle and adipose tissues. In beef value-based marketing, carcass value is largely determined by amount of product (carcass weight), percent of boneless trimmed retail product (yield grade), and intramuscular fat deposition (quality grade).

Effects of prepartum nutrition on postnatal muscle and

adipose tissue development of ruminants are not clearly elucidated, and further research is needed. Furthermore, effects of source of energy in gestation diets on pre-and postnatal growth development, and carcass composition are unknown. Effects of maternal prepartum nutrition on dam performance In late-gestation and early lactation, dams have the highest energy requirements. In spring-calving beef herds and sheep flocks, forage available during the winter does not typically meet energy and protein requirements of the dam. Previous research at Ohio State University (OSU) reported pasture quality during late winter and early spring was the lowest when a spring-calving cow has her greatest nutritional demand in late gestation and early lactation (Schoonmaker et al., 2003). Furthermore, during times of drought, supply of forage can be limited and expensive. Because feed costs represent the

3

largest portion of expenses in a flock or herd, identifying economical alternatives for protein and energy sources is important. A significant increase in maternal energy requirements occurs in late gestation, but only half of the energy demand can be attributed to the gravid uterus (Ferrell et al., 1976; Scheaffer et al., 2001). Visceral tissues represent approximately 6% of empty body weight but are responsible for consuming 41% of total energy expenditure in gestating beef cows (Ferrell, 1998).

Increased maternal energy needs may be met through

increased feed intake, decreased maintenance energy expenditure, utilization of stored body reserves, decreased external work, or decreased energy loss by excretion (Stock and Metcalfe, 1994).

Sufficient energy reserves during this period are most commonly

monitored by body condition score of the cow.

Mobilization of maternal nutrient

reserves may offset deleterious effects of restricted nutrition during gestation; thereby, meeting energy needs to maintain body condition of dams during late gestation is critical. Supplementation Protein and energy supplementation are most common in winter-feeding of forage-based diets or when cattle are grazing low-quality forages. To achieve optimal use of these forages, and meet the animal’s nutritional needs, often it is necessary to provide supplemental nutrients (Caton and Dhuyvetter, 1997).

The cost of dam

supplementation can be offset by increasing weaning weight and by increasing the percentage of live calves at weaning (Stalker et al., 2006). Feed by-products, which are high in protein or energy, are commonly used as economical supplements for gestating cows.

4

When feeding low-quality forages, it is common to have inadequate ruminal N concentrations. Deficient ruminal ammonia may limit microbial crude protein synthesis and growth by limiting microbial fermentation of fiber, which reduces digesta outflow, and forage intake (Egan, 1980).

Protein supplementation often increases cattle

performance by increasing dry matter intake and forage digestibility (Marston et al., 1995; Gilbery et al., 2006). In comparison to corn, the nutrient composition of DDGS is high in crude protein content (approximately 20-23%, DM basis) of which the majority is undegraded in the rumen. In mature cows, benefits of protein supplementation often include a decreased loss of body weight and body condition score. Energy supplements can be starch, fat, or fiber based. In low quality forage diets, supplementation with highly digestible fiber as an energy source may be more advantageous than starch (Summer and Trenkle, 1998) and fat (Oldick and Firkins, 2000), because these energy sources can inhibit fiber digestibility. Summer and Trenkle (1998) compared supplementation of DDGS, corn gluten meal, and corn with low and high quality forages. Dried distiller grains had the greatest dry matter digestibility with lower quality forages, whereas corn had greater dry matter digestibility when fed with high-quality forage. Oldick and Firkins (2000) reported ruminal neutral detergent fiber digestibility was decreased and efficiency of microbial protein synthesis was increased when fat was fed in forage-based diets. In feedlot studies, DDGS has been shown to have similar or more energy than corn (Stock et al., 1999). Therefore, the quality of forage, type of energy supplement, and the combination of the two will determine digestible energy intake and performance in gestation diets. Alternative energy sources

5

Limit feeding corn-based diets in late gestation has been demonstrated to be an economic alternative to hay feeding for beef cattle (Loerch, 1996) and sheep (Susin et al., 1995). Winter grazing of stock-piled forages is also an economical alternative to hay feeding (Schoonmaker et al., 2003). Studies conducted at Ohio State University reported that limit-feeding corn in gestation diets of mature cows, and heifers, had no detrimental effects on subsequent cow performance or conception rate; however, a 3 to 5 kg increase in the birth weight of progeny was consistently observed. Dried distiller grains, although low in starch, are high in digestible fiber and contain 11-12% fat. Thus, DDGS are an attractive source of supplemental energy to forage-based diets. Recent studies in steers have reported improved fiber digestion with the addition of corn DDGS with medium quality hay (Gilbery et al., 2006). No adverse effects were noted when DDGS were fed at up to 1.2% of BW (Leupp et al., 2009). Improved average daily gain and reduced forage intake in heifers consuming both low and high quality forage diets up to 0.4% BW were reported by Morris et al. (2005) and Loy et al. (2007). These studies suggest DDGS are an effective energy supplement in forage-based diets. Limit feeding DDGS and wet corn gluten feed (WCGF) were investigated in lactation diets by researchers in Illinois. In one study, DDGS and WCGF replaced hay in lactation diets and resulted in cows fed DDGS gaining more weight and producing less milk than those cows receiving the limit-fed WCGF (Shike et al., 2004). In a second study comparing these by-products during lactation, ground corn stalks (a low quality forage) were used instead of hay and showed similar weight gains and milk production for both fiber sources (Faulkner et al., 2005). These studies indicate ethanol by-products

6

are an excellent energy source and may be an alternative to corn in limit-fed gestation diets, however in these studies limit-fed DDGS was only investigated postpartum. In order to meet requirements (NRC, 2000), supplementation of protein is needed if cows are limit-fed corn, because corn has low protein content (10%) and feed intake is being restricted. Rossi et al. (1999) reported poultry manure was a more economic alternative to soybean meal as a protein supplement, by significantly decreasing feed costs with no negative effects on cow performance. Investigating more economical protein sources may still be needed, because public perception of non-vegetarian feed sources for ruminants is predominantly negative. One distinct advantage of DDGS to corn, in limit-fed diets, is a greater protein concentration, which would eliminate the need for additional protein supplementation to meet protein requirements. Thereby, DDGS could meet both energy and protein requirements of cows in a limit-fed diet, while potentially being more cost effective than corn. Milk production and composition Milk production postpartum can be influenced by prepartum nutrition of the dam. If milk production is changed by prepartum diets this could be a confounding factor in the ability to measure the effects of prepartum energy source on postnatal growth of calves. In postpartum beef cows, several investigators have reported increased energy intake during gestation corresponded with increased milk production (Perry et al., 1991; Jenkins and Ferrell, 1992; Marston et al., 1995) and calf weaning weights (Richards et al., 1986; Spitzer et al., 1995). Cows receiving an energy-deficient gestation diet (8.4 Mcal of DE/d) verses a high-energy diet (19.3 Mcal of DE/d), had lower milk production (Corah et al., 1975). Additionally, cows allowed limited vs. ad libitum grazing access

7

prepartum had a 9% decrease in early lactation milk production (Kearnan and Beal, 1992). Lalman et al. (2000) reported feeding high-energy diets postpartum reduces negative effects of prepartum nutrient restriction on milk production but does not completely reverse those effects. A positive correlation was reported by Collier et al. (1982) between calf birth weight and subsequent milk yield, suggesting that factors associated with calf birth weight may also influence postpartum milk yield.

If limit-fed corn increases birth

weights, then this would suggest milk production may be altered by prepartum diets. Only one study has measured subsequent milk production in comparing limit-fed corn with a forage-based diet during prepartum and results reported a trend for a reduction in milk production in Holstein cows the first 28 d in lactation (Driedger and Loerch, 1999). A few studies have directly, and indirectly, measured effects on milk production from fat supplementation during gestation. Small et al. (2004) investigated limit-fed corn diets with or without addition of fat, and reported post-weaning growth was not different, suggesting milk production was not affected. This concurs with Alexander et al. (2002) where no difference in milk production was reported between fat supplemented and nonfat supplemented cows. These few studies indicated that feeding an energy source during gestation may result in different effects on postpartum milk production in cattle. Calf and lamb postnatal immune response has been associated with calf/lamb immune status postpartum, possibly due to immunoglobulin G (IgG) availability in colostrum (Hough et al., 1990). Over and under nutrition of ewes resulted in decreased IgG concentration, nutrient content, and volume of colostrum in milk (Swanson et al., 2007). Studies have reported prepartum restriction of nutrients resulted in a decrease in

8

colostral IgG (Shell et al., 1995) and absorption of IgG by calves. Effective passive transfer of IgG in colostrum is vital to calf health and immunity (Perino et al., 1993). Serum IgG concentration was classified according to Perino et al., (1995) as adequate (> 16.00 mg/dL), marginal (8-16 mg/dL) or inadequate (< 8.00 mg/dL).

Decreased

absorption of IgG was found in lambs from over nourished ewes (Hammer et al., 2007), which also resulted in higher lamb mortality. In beef cattle, milk composition was altered by pre-partum supplements containing fat (Tjardes et al., 1998; Alexander et al., 2002; Bottget et al., 2002), while milk production only increased in one study (Tjardes et al., 1998).

Lammoglia et al.

(1999) reported decreased morbidity and mortality in calves with prepartum supplementation of fat. Calves from fat supplemented cows, that were limit-fed corn, had a higher total serum IgG concentration suggesting improved passive transfer (Small et al., 2004). These calves also had altered plasma fatty acid profiles with an increase in conjugated linoleic acid in fat supplemented calves. These fatty acids have been shown to play a role in immune function (Hwang, 2000; Sucher et al., 2000). Therefore, it may be possible that increased fatty acids associated with immune function could alter early calf immune status. Compromised calf or lamb immunity at parturition may have long lasting and profound effects on health. Calves with lower levels of IgG and total plasma protein at 24 h post-partum had a greater incidence of pre-weaning and feedlot morbidity and mortality (Wittum and Perino, 1995).

Morbidity post-weaning is well documented to

depress feedlot performance and carcass quality, more specifically intramuscular fat (Roeber at al., 2001; Duff and Gaylean, 2007). Therefore, the long-term impacts animal

9

health may not only affect growth performance, but could have a significant impact on intramuscular fat accretion. Nonetheless, research has not been published to demonstrate prepartum nutrition effects on health status of offspring and subsequent growth and carcass characteristics. Reproductive performance Previous studies have established the importance of prepartum nutrition on subsequent reproduction in beef cattle (Randel, 1990; Short et al., 1990, Dunn and Moss, 1992). During early lactation, energy demands are greatest for the cow and the negative impacts of inadequate nutrition during late gestation are difficult to reverse by postpartum nutrition (Hess et al., 2005). In a review of nutrition control of reproduction, Hess et al. (2005) concluded that pre-partum supplementation has a greater impact on length of post partum anestrus than does post partum supplementation.

Energy intake and body

condition may account for a majority of the differences in reproductive performance of beef cattle. Energy from lipid supplementation of vegetable sources during late gestation has been reported in limited studies to improve reproductive efficiency (Bellows et al., 2001; Hess et al., 2005). Dried distillers grains contain a relatively high fat content (6-12%) compared to other commonly used energy sources used in ruminant diets. More specifically, DDGS supplemented to first-calf heifers in isocaloric diets improved first AI conception and overall pregnancy rates (Martin et al., 2007). However, in isocaloric prepartum diets of limited-fed corn with or without supplement fat, conception or overall pregnancy rates in cows did not differ (Small et al., 2004). In comparing limit-fed corn to ad libitum hay, overall conception rates were not different. In contrast, when compared to stockpiled

10

forage, conception rates tended to be lower for limit-fed cows (Schoonmaker et al., 2003), while body condition score was higher. Results have not been consistent in studies investigating fat supplementation preand postpartum. Houghton et al. (1990) indicated that cows in moderate body condition at parturition that maintained their condition until breeding had higher pregnancy rates than cows that were thin at calving or excessively conditioned at breeding. If body condition score is adequate this may suppress the impact of additional fat when cows are already at peak reproductive performance.

When Hess et al. (2005) reviewed the

published literature, they found the benefit of fat supplementation pre-partum improved pregnancy rates 10.5%; however, less of a response was found with cows in adequate body condition and in herds with pregnancy rates greater than 90%. Lack of a response could also be attributed to a reduction of energy supplied to the cow, since excessive lipid can decrease fiber digestion (Jenkins, 1993). Further research is needed to determine if the effect of fat supplementation is due to increased energy content of the diet or metabolism of fatty acids. Comparing starch, fiber, and fat energy sources in isocaloric diets would provide beneficial information regarding effects of fat supplementation on reproductive performance to answer this question. Furthermore, prepartum supplementation may have maternal imprinting effects on the female progeny. Heifers from dam’s supplemented prepartum had greater weaning and yearling weights, increased pregnancy rates, and a shorter calving interval than their non-supplement counterparts (Martin et al., 2006). Growth rate, body energy reserves,

11

and nutrient intake have a great impact on ovarian function in beef cattle (Wettermann and Bossis, 2000), which may be influenced by fetal programming. Effects of maternal prepartum nutrition on offspring Dr. David Barker was the first to state the hypothesis of fetal programming (Barker et al., 1993; Godfrey and Barker, 2000), which he defined as a maternal stimulus or insult at a critical period of development of the fetus that can have lifelong impacts postnatally. Maternal diet, one environmental factor in fetal development, has been documented to have long-term effects on nutrient partitioning in fetal development (Godfrey and Barker, 2000; Wallace et al., 2004; Wu et al., 2006).

In food animal

species, global nutrient restriction in the maternal diet during gestation has been reported to have postnatal impacts of decreased health, slower growth rate, increased fat deposition, reduced muscle mass, and reduced meat quality in progeny (reviewed by Wu et al., 2006). Few studies have investigated the moderate changes in maternal nutrition most commonly found in livestock production, and their effects on the progeny’s postnatal development. No studies have investigated the effects of energy source (at isoenergetic intake) on postnatal development. Fetal development When the dam maintains adequate body weight and body condition, the fetal nutrient supply will be adequate for growth and development. Therefore, meeting the dam’s nutrient requirement is important to ensure adequate nutrient supply to the fetus. Individual fetal tissues develop at different times during gestation, and timing of a maternal stimulus or insult to the fetal nutrient supply can result in different responses in postnatal growth and body composition (Figure 1.1). In cattle and sheep, 90% of the fetal

12

body weight, mostly due to skeletal muscle growth, is achieved the last 40 days of gestation (Bell et al., 2005a).

Figure 1.1. Sheep conceptus growth and development in gestation and periods of specific organ development that can be influenced by maternal nutrition.

CV =

cardiovascular system (adapted from Symonds et al., 2007).

Fetal nutrient supply Metabolism of the dam changes during gestation, to meet the needs of the conceptus. In many production situations, maternal body tissues are catabolized in late gestation to meet the needs of the placenta and fetus (Robinson et al., 1999). To meet these energy demands, the dam increases hepatic gluconeogensis by mobilizing glycerol 13

from fat; amino acids from muscle; and lactate from muscle. These metabolic changes during late gestation can cause moderate insulin resistance.

Evidence of insulin

resistance in ewes in late gestation occurs in adipose tissue resulting in decreased lipolysis, and in muscle by less GLUT 4 expression resulting in decreased uptake of glucose (Petterson et al., 1994; Ehrhart et al., 1998; Ehrhart et al., 2001).

Moderate

nutrient restriction has been shown to exaggerate insulin resistance in maternal adipose and muscle tissues in sheep (Petterson et al., 1993). The placenta produces hormones during gestation, including progesterone, oestradiol-17β (E2), and placental lactogen. The role and mechanisms of action of these hormones, in metabolic adaptations of the dam during pregnancy, have not been well explained (Metcalfe et al., 1988). Progesterone has been proposed to alter metabolism of the dam by increasing the plasma insulin:glucagon ratio and amplifying peripheral insulin resistance in non-adipose tissue (Bell et al., 2005a). Estradiol has been associated with changes in lipid metabolism in late-gestation ruminants (Forbes, 1986), but infusion of elevated levels in sheep did not result in any response in glucose or NEFA metabolism (Andriguetto et al., 1996). Placental lactogen may also play a role in amplifying insulin resistance in late gestation by increasing insulin secretion, protein conservation, and lipolysis while decreasing glucose utilization in the maternal tissues.

One unique

characteristic of placental lactogen is the peptide cross-reacts with both growth hormone and prolactin receptors in ruminant tissues (Gertler and Djiane, 2002). Production of these hormones can change with stage of gestation, and therefore, could have different effects at different stages in gestation (Ferrell et al., 1989). Limited research has been

14

conducted investigating the effects of maternal nutrition and production of these pregnancy-related hormones. Placental size and function are major determinants of fetal growth in late gestation, and are largely determined by maternal nutrition and body weight. Fetal nutrient supply is dictated by the placenta’s capacity to transfer, utilize, and modify substrates (Owens, 1991). The majority of the placental growth occurs in early to midgestation prior to greater demands by the fetus for substrates for growth in late gestation. However, placental capacity to supply substrates by such characteristics as surface area, blood flow rates, and glucose transfer capacity continues to increase until the end of gestation. Cotyledonary weight and placentomal surface were reduced which resulted in reduced fetal weights, when cows were nutrient restricted during early gestation (Long et al., 2009). In cows, the placenta consumes 40 to 60% of gravid uterus consumption of oxygen and glucose in mid- to late-gestation (Ferrell and Ford, 1980; Ferrell et al., 1983). The placenta is a major competitor for these nutrients in late gestation, when fetal demand for substrates is both substantial and increasing. The placenta needs these nutrients for the production of hormones and energy-dependent transportation of substrates such as glucose and amino acids. The primary substrates needed to meet fetal energy and protein demands are oxygen, glucose, amino acids, and lactate.

Other

nutrients such as long-chain fatty acids, acetate, and keto-acids are small contributors to the energy supplied to the fetus. In ruminants postnatally, 65% of the energy supply is from volatile fatty acids (VFAs; acetate, propionate, and butyrate); however the

15

contribution of these VFAs to fetal metabolism is small. The contribution of acetate has been estimated to be between 10-15% of fetal oxygen consumption (Bell et al., 2005a). Glucose supply to the fetus is largely determined by maternal arterial glucose concentration. Studies in vivo controlling glucose transfer and utilization by glucose and insulin clamps in late-gestation sheep have shown placental glucose transfer and uptake are independent of insulin concentrations in the maternal and fetal circulations (as reviewed by Hay, 2006). The primary glucose transports used by the placenta are GLUT1 and GLUT-3 (Ehrhart and Bell, 1997). The major portion of glucose transport is hypothesized as GLUT-3 due to a significant increased in GLUT-3 protein production during gestation; to a low Km of GLUT-3; and to the location of GLUT-3 on the maternal-facing layer of the placental (Bell et al., 2005). Additionally, the establishment of the placenta’s vascular system is critical to the development of the fetus by contributing to substrate supply.

During gestation,

caruncular vascularzation is primarily developed in mid-gestation (d 30 to 125) in cattle (Ferrell et al., 1976; Reynolds et al., 1995). During gestation over and undernourishment of ewes have been associated with a reduction in placental vascularity and angiogenic factors known to affect vascular growth (as reviewed by Redmer et al., 2004). Both of these models have been shown to result in lambs with reduced birth weights compared to lambs whose dam’s were fed to meet nutrient requirements. A comparison of early gestation nutrient restriction in ewes, adapted to different nutritional planes (limited nutrition vs. adequate nutrition), has provided evidence that placental efficiency can be influenced by this adaptation, regardless of similar nutrition (Vonnahme et al., 2006; Jobgen et al., 2008). Ewes that were adapted to harsh range

16

conditions, and limited nutrition, and were then fed either a nutrient restricted diet or an adequate diet had a similar conceptus growth and fetal concentration of amino acids (Jobgen et al., 2008). These results are in contrast to ewes receiving adequate nutrition in which placental and fetal weight was reduced with maternal nutrient restriction in early gestation (Vonnahme et al., 2006; Ford et al., 2007). Collectively, these results suggest that maternal nutrition can alter placental growth, vascularity, and efficiency, which can ultimately affect fetal development. Fetal Skeletal Muscle Development Skeletal muscle mass growth is a combination of varying degrees of three factors: increased muscle cell number (hyperplasia); increased muscle cell size (hypertrophy); or changes in muscle synthesis and/or breakdown.

Muscle mass is largely determined by

the number of muscle fibers and size of muscle fibers. Several factors can influence fiber number and size such as; gender, breed, genetics, nutrition, physical activity, and growth promoting agents such as hormones (Rehfelt et al., 2004). The quantity and quality of meat can be affected by the composition and number of skeletal muscle fibers. Muscle fiber hyperplasia, in mammals, is largely completed during early gestation, and is fixed by birth. During prenatal muscle development, primary myofibers are formed, followed by the formation of secondary myofibers (Beermann et al., 1978). Primary myofibers have peripherally located myofibrils surrounding an axial core of nuclei and cytoplasm (Swatland, 1973). The secondary myofibers are derived from muscle precursor cells, which are initially maintained in a proliferating, undifferentiated state. Those precursor cells differentiate into myoblasts and fuse to form secondary myofibers parallel to primary myofibers.

17

The ability to manipulate fetal muscle fiber number by environmental factors may be possible. Results reported by Fahey et al. (2005a) indicated the majority of muscle differentiation and formation takes place prior to d 85 of gestation for sheep, with myoblast proliferation mainly occurring before this time. This corresponds in the bovine muscle cell to about 125 days of gestation.

This suggests it may be possible to

manipulate the number of muscle fibers formed by targeting treatments during this proliferation stage immediately before the period of major fiber formation. Coefficients of heritability estimated for muscle fiber number range from 0.12 to 0.88 (Rehfeldt et al., 1999), demonstrating the muscle fiber number is not exclusively determined genetically as previously had been presumed. Adequate nutrition is essential for skeletal muscle development and severe undernutrition in pigs has resulted in a reduction in muscle fiber numbers (Wigmore and Strickland, 1983). On the other hand, a dramatic increase in nutrient availability to the embryos, achieved by growth hormone treatment of sows during early pregnancy, increased muscle fiber number in offspring (Rehfeldt et al., 2004). Alteration of the insulin-like growth factor levels and system, is hypothesized to contribute to changes in muscle fiber number (Rehfeldt et al., 2004). Once these muscle fibers are formed, their numbers cannot be altered. Although factors in late gestation and postnatally, will not affect muscle fiber number, many factors affect the size of fibers (Rehfeldt et al., 1999). Postnatal growth depends on a special pool of cells (called satellite cells) that proliferate, synthesize myofibrillar proteins, and fuse with existing muscle fibers, resulting in an increase in muscle cell size (Morgan and Partridge, 2003). Decreases in muscle fiber size have been accompanied by a reduction in muscle nuclear number or DNA content, but with increased DNA/protein or nuclear

18

cytoplasm ratios as reviewed by Rehfeldt et al. (2004). An inverse relationship exists between muscle fiber number and size. Additionally, although muscle hypertrophy will contribute to an increase in muscle mass, when enhanced, this can have detrimental impacts on tenderness and meat quality. A reduction in skeletal muscle satellite cells, but not muscle cell number, has been reported in rat pups whose dams were nutrient restricted during pregnancy (Beermann, 1983a; Beerman et al., 1983b). When ewes experienced a 70% nutrient restriction throughout gestation, their progeny had reduced muscle weight associated with reduced fiber diameter and sarcomere length, but similar muscle fiber number (Nordby et al., 1987). These results suggest that maternal nutrition may exhibit a greater influence on hypertrophy of fetal muscle than hyperplasia.

In contrast, a more recent study

investigating timing of nutrient restriction on fetal skeletal muscle development in sheep reported that maternal diet does affect fetal muscle cell number. Fetuses from dams nutrient restricted in either early or late gestation had less myofiber density as compared to fetuses from dams fed to NRC nutrient requirements (Costello, 2008). Muscle mass is maintained through constant turnover of myofibrils. Rate of protein degradation is the predominant factor in turnover of muscle proteins. The calpain and the ubiquitin-proteasome systems play crucial roles in the control of muscle protein degradation. A few studies have investigated the effects of maternal nutrient restriction on these systems. However, it is not known if source of maternal nutrition (i.e., fiber, starch or fat) can play a role in fetal protein degradation rates Calpain is a calcium-dependent protease system, which is regulated by Ca2+ concentration and by binding calpastatin, its specific inhibitor (Goll et al., 2003). The

19

calpain protease system initiates protein degradation of muscle, but the level of calpastatin has the greatest effect on the rate of protein breakdown. Calpastatin activity can be influenced by high dietary protein intake (Helman et al., 2003) and by maternal nutrient restriction (Du et al., 2004). Du et al. (2004), reported calpastatin was downregulated in dam skeletal muscle while fetal muscle was upregulated in response to nutrient restriction in cattle. Mammalian target of the rapamycin (mTOR) signaling pathway is critical for sensing nutrient-stimulated muscle growth through phosphorylation of key factors involving protein synthesis (Bodine et al., 2001). Rapamycin activity is down regulated in cells when the supply of nutrients, especially amino acids, is insufficient (Bodine et al., 2001). Maternal nutrient restriction showed a similar response as Du et al. (2005) with acceleration of protein degradation in muscles of pregnant cows but not in fetal muscle. However, mTOR was down-regulated in both cow and fetal muscles tissue. Similar results were reported by Zhu et al. (2004) in sheep. Lower signaling of mTOR signaling in nutrient-restricted fetuses may reduce the proliferation of myoblasts and thus, reduce the formation of secondary myofibers. The phenotype of a given muscle fiber is specified during muscle development, but fibers are capable of changing their type in response to adjustments in functional demands.

The functional classification of muscle type is based on the following

parameters of the contractile response: the rate at which tension develops and ability to cope with energy consumption (resistant to fatigue vs. fatigable). From this criterion, three main types of fibers can be identified; 1) slow and fatigue resistant, 2) fast and fatigue resistant, and 3) fast and fast fatigable.

20

Muscle fiber type may be of great interest in bovine muscle, based on the assumption it may play a role in determining meat quality and tenderness. A greater percentage of fast glycolytic fibers have a greater rate of post-mortem aging and fiber type composition varies with rearing conditions and genotype (Jurie et al., 1995). Physiological status and feeding also may affect fiber type composition (Brandstetter et al., 2000). Maternal nutrient restriction in late gestation (d 104-term) has been reported to reduce the proportion of slow-twitch muscle fibers in offspring in sheep (Costello et al., 2008). In contrast, nutrient restriction during mid-gestation (d 30-70) increased the number of slow-twitch fibers and decreased the number of fast-twitch fibers (Fahey et al., 2005b).

The conflicting results in the previous two studies may be due to timing of the

nutrient restriction in relation to stages of muscle development. Fetal development of adipose tissue Approximately 80% of fetal adipose tissue is deposited in the final few weeks of gestation, but the development of these adipocytes start earlier in gestation (Symonds et al., 2007).

Initiation of adipogensis during fetal development begins in mid-gestation

(Gnanalingham et al., 2005); however growth of adipose tissue during the remainder of fetal development and postnatally is due to both hypertrophy and hyperplasia (Feve, 2005).

Postnatally, new adipocytes are rarely generated in intramuscular fat, and

hyperplasia primarily occurs in visceral and subcutaneous fat depots (Tong et al., 2008). Enhanced adipogensis in fetal muscle produces a large number of adipocytes in skeletal muscle that predisposes the offspring’s muscle to accumulate intramuscular fat due to hypertrophy of existing adipocytes (Zhu et al., 2008). An increased number adipocytes

21

has been associated with skeletal muscle insulin resistance (Aguiari et al., 2008). Thus, changes in insulin resistance of fetal tissue could potentially impact adipogensis. Mechanisms controlling adipogensis in fetal muscle have not been well elucidated. Overnutrition of the dam can cause an inflammation response, which is proposed as one reason for increased adiposity in fetal muscle by Du et al. (2009). Inflammation signaling by the nuclear factor-Κ B (NFKB) pathway has been associated with decreased myogenesis (Ardite et al., 2004), and upregulation of fat cell differentiation (Berg et al., 2004).

Additionally, Tumor necrosis factor-α (TNF), a

hallmark of an inflammatory response, has been reported to reduce AMP-activated protein kinase (AMPK) activity in skeletal muscle (Steinberg et al., 2006). In beef cattle studies, AMPK activity was positively associated with muscularity and negatively associated with number of intramuscular adipocytes (Underwood et al., 2007; Underwood et al., 2008b), indicating the AMPK may shift myogenesis to adipogensis during fetal development. However, few studies have investigated the effects of maternal nutrition on these specific pathways, and fetal adipose and muscle tissue development. Lambs and calves are born with almost 100% brown adipose tissue (BAT), unlike other species, which are born with brown and white adipose tissue (WAT; Alexander and Bell, 1975).

Brown adipose tissue is responsible for nonshivering thermogenesis and

can be critical to postnatal survival in livestock production in colder climates. Brown adipose tissue is used within the first few days postnatal, and it has been suggested BAT may serve as precursors for WAT. Postnatally, WAT represents the majority of the fat deposited, and is found in four depots within the body: subcutaneous (external; backfat);

22

internal organs (perirenal, visceral, mesenteric; internal); intermuscular (between the muscles; seam); and intramuscular (within the muscle; marbling). In vivo studies, in cattle and sheep, have provided evidence that maternal diet can impact postnatal fat deposition in their progeny. Ewes who experienced early gestational nutrient restriction (20-80 d gestation) and were then fed a diet meeting requirements, resulted in more adipose deposition in the fetus at parturition (Bispham et al., 2003), and at 1 year of age (Gardner et al., 2005). Adequate or increased maternal intake in lategestation appears to shift nutrients to more muscle development and less adipose tissue deposition in the fetus (Budge et al., 2000; Symonds et al., 2004). Additionally, steer progeny from cows, which were nutrient restricted during gestation, had less external marbling, and internal fat deposition, at a similar age indicating maternal plane of nutrition may alter partitioning of fat deposition within the animal (Underwood et al., 2008b). Fetal programming of insulin resistance Skeletal muscle, comprising 40-50% of body mass, is the primary tissue for the utilization of glucose and fatty acids (Goodpaster and Wolf, 2004). As a result, reduced muscle mass will decrease the metabolism of glucose and fatty acids in response to insulin stimuli, and thus will predispose offspring of nutrient-restricted mothers to diabetes and obesity. This process has received much attention, since human infants who are small at birth were shown to have a greater risk for type-2 diabetes (Godfrey and Barker, 2001). It has been hypothesized that long-term health implications, are the results of a disturbance in fetal development, which can lead to ’programming’ of an increased predisposition to various disease syndromes during later postnatal life, and may

23

alter body composition. Whereas this predisposition may be detrimental to human health, it may allow enhanced development of the intramuscular fat depot in ruminants, which would be advantageous. In fetal muscle, a large number of mesenchymal stem cells exist. Although a majority of these mesencheymal stem cells differentiate into myotubes, these cells are also capable of differentiation into either adipocytes or fibroblasts. Overall increased adiposity or adipogensis, especially intramuscular triglyceride and visceral fat in humans, has been associated with decreased insulin sensitivity by muscle cells (Lewis et al., 2002). The mechanisms accounting for the relationship between muscle triglyceride accumulation and insulin resistance is not known. Skeletal muscle is the most abundant insulin-sensitive tissue, comprising 40-50% of human body mass and responsible for approximately 20-30% of resting oxygen consumption, and handles 75-95% of all insulin mediated glucose disposal (Stump et al., 2006). Any changes in muscle mass, metabolic rate, and/or response to hormones and other circulating factors would significantly affect the body’s overall energy stores and metabolism and could be ‘programmed’ in the fetus by maternal nutrition during gestation. Insulin resistance is associated with impaired insulin-signaling that results in inflexibility in transitioning between lipid and carbohydrate fuels (Stump et al., 2006). Lipid accumulation in skeletal muscle may indicate an imbalance between supply and oxidation of lipid. This accumulation may be partially explained by a reduced capacity to oxidize fatty acids, due to impaired mitochondrial content and/or function (Stump et al., 2006). Rats selected for reduced skeletal muscle mitochondrial capacity develop risk factors consistent with insulin resistance (Wisloff et al., 2005). Greater insulin sensitivity

24

is observed in highly oxidative (i.e. type I or ‘red’ muscle) compared to more glycolytic (type 2 or ‘white’) skeletal muscle fibers. This is consistent with the finding that type 2 fibers are more abundant in humans with components of insulin resistance (Lillioja et al., 1987). Therefore, factors that affect skeletal muscle mass and type of muscle fiber could result in lower insulin sensitivity and increased intramuscular fat in ruminants. Nutrient restriction imposed on ewes in early gestation resulted in progeny displaying hyperglycemia and an altered insulin response to a glucose challenge (Ford et al., 2007; Effertz et al., 2007). Insulin resistance has also been reported in lambs from ewes fed restricted nutrients during late gestation and was associated with increased adipose mass and reduced expression of GLUT 4 expression in adipose tissue (Gardner et al., 2005). A reduced initial insulin response, which in humans has been correlated with patheogenesis of type 2 diabetes (Leahy, 2005), was reported in male progeny from ewes with a low (2 or less) body condition score (Cripps et al., 2008). However, none of these studies have investigated effects of insulin resistance on partitioning of fat to different fat depots within the body. Fetal programming of postnatal growth Greenwood et al. (2000) reported low birth weight lambs had less muscle weight gain during postnatal growth. This result was in association with an increase in the amount of DNA, in muscle indicative of fewer myonuclei but not by fewer numbers of myofibers. These low birth weight lambs were from ewes well-fed throughout pregnancy and the restriction of growth is mostly attributable to placental limitation of fetal growth (Greenwood, 2000). Hunt (1995) proposed that severe fetal growth retardation of lambs, and other ruminants, may result in a similar number of myofibers as in well-grown

25

fetuses at completion of myogenesis, but with fewer nuclei per fiber. The results from these studies suggest that permanent impairment of the lean growth potential of sheep may be imparted by a restricted supply of energy to the fetus during pregnancy. Greenwood et al. (1998) proposed that metabolic systems require a longer period of adaptation to postnatal life in low birth weight lambs. In lambs, low birth weight had the long-term effect of elevated insulin levels, which may be associated with a degree of insulin resistance due to a markedly elevated weight-specific nutrient intake. The authors hypothesized that these lambs may require more amino acids and less dietary lipid, compared to heavier newborns during the early postpartum period (Greenwood et al., 2002). These lambs were also less efficient and had more body fat, indicating carry-over effects of prepartum nutrition on energy metabolism and body composition. The IGF system regulates growth and development of domestic animals (Bell et al., 1998). Early in development, the ligands of the growth factor system, IGF-I and –II, function primarily in autocrine and paracrine fashion. By late prenatal life, however, the endocrine arm of the IGF system is activated (Daughaday and Rotwein, 1989; Stewart and Rotwein, 1996). Nutrition and growth hormone (GH) can alter plasma IGF-I in late gestation (Hua et al., 1993; Weller et al., 1994; McGuire et al., 1995). Undernourished, low birth weight lambs appear to have a delayed maturation of their endocrine insulinlike growth factors system (Rhoads et al., 2000). In ruminants, birth is associated with maturation of the somatotropic/insulin growth factor (IGF) axis, which has an important role in the regulation of anabolism and catabolism in skeletal muscle (Gluckman et al., 1999).

Long-term consequences of prenatal growth retardation in low birth weight

lambs, on endocrine and metabolic development, are not well understood.

26

Fetal programming on livestock production traits Mechanisms by which nutrition, during pregnancy, affect growth of offspring are still not clearly understood, nor are the long-term impacts on livestock production traits measured postnatally. Considerable evidence indicates that prepartum nutrition impacts calf birth weight (Collier et al., 1982; Boyd et al., 1987), milk production (Holst et al., 1986), and calf immunoglobulin production (Blecha et al., 1981). These factors can influence the survival, health, and growth rate of offspring. Sheep and cattle models have been used to test the Barker hypothesis investigating global under- and over-nutrition in maternal diets. Degree and timing of nutrient restriction can produce different outcomes for postnatal growth and production traits.

Nutrient restriction (55%) in early gestation (d 32 to 115) of cows did not

influence birth weights; postnatal growth; or carcass characteristics of calves (Long et al., 2008). In contrast, Underwood et al. (2008b) reported greater postnatal growth and feed efficiency in steers from cows nutrient restricted during a similar period of gestation (d 31 to 120). Nutrient restriction (55%) during early to mid-gestation in sheep (d 28-78) resulted in male offspring having similar birth weights, but lighter weights at slaughter, greater amounts of internal fat, and less muscle mass (Ford et al., 2007). In these studies, nutrient restriction appears to have provided adequate energy for fetal growth, possibly at the expense of the dam’s tissue because nutrient partitioning during pregnancy favors the fetus at the expense of the dam (Barcroft, 1946).

Nevertheless, these studies provide

evidence of long-term affects on postnatal growth and body composition which may indicate a change in how the fetus is ‘programmed’ to partition nutrients postnatal.

27

Studies investigating protein supplementation of cows during late gestation have reported long-term impacts on their progeny (Stalker et al., 2006; and Martin et al., 2007; Larson et al., 2008). In these studies, steer progeny from dams supplemented protein had similar weights at birth, but heavier weaning, final body, and hot carcass weights as compared to steers from dams not supplemented with protein. Protein supplementation of the dams also resulted in carcasses from steer progeny with a higher marbling score and higher percentage of USDA Choice or higher quality grades (Larson et al., 2008). Heifer progeny from the dams supplemented with protein had heavier body weights at weaning and breeding. Although age at puberty and the percentage cycling before the breeding season were similar among heifer progeny, a greater proportion of heifers from dams supplemented with protein calved within the first 21 d of the heifer’s first calving season. Collectively, these results provide evidence that an individual component of the maternal diet, such as protein, could impact heifer progeny reproductive development as well as steer progeny growth and carcass characteristics. The amount of prepartum energy can influence calf birth weight during the last 100 d of gestation, when fetal growth is at its greatest, and can influence postnatal growth (Boyd et al., 1987). Providing a high vs. low energy diet during late gestation in beef cattle was reported to increase calf birth weight and subsequent weaning weight (Corah et al., 1975). Source of energy (limit-fed starch diets) in late-gestation diets also appears to impact fetal growth and development. Loerch (1996) reported that heavier birth weights occurred from cows limit-fed corn; however inconsistent results were reported for weaning weight (Loerch, 1996). No other data have been published regarding postnatal growth of calves, when cows in gestation were limit-fed concentrate diets with differing

28

sources of energy. However in contrast, Susin et al. (1995) reported similar birth weights and postnatal growth of the lambs from ewes limit-fed, corn-based gestation diets similar to the studies conducted in cows (Loerch, 1996). Increased fetal glucose supply has been associated with larger lamb birth weights (Stevens et al., 1990). When the proportion of concentrate (starch) is greater than forage, propionate, a precursor to glucose, is greater.

Propionate is converted to glucose, via

gluconeogensis in the liver and enters the maternal blood supply and is the preferred energy source by the fetus (Bell et al., 2005b). Increased maternal glucose supply may increase the supply of glucose to the fetus, thereby increasing fetal growth, and hence, larger birth weights. The current literature published on studies investigating the impacts of maternal diet in ruminants on progeny has only used animal models to test the effects of global undernutrition, global overnutrition, and protein supplementation. To our knowledge no one has investigated specific energy sources differing in starch and glucose precursors in maternal diets on their impacts on postnatal growth and body composition in beef and sheep. Research on alternative feeds and feeding practices, which could potentially reduce cost of production without sacrificing cow or calf production traits are needed. The impacts of these management decisions on growth and carcass composition of offspring are unknown, but there is evidence that postnatal growth and development can be affected by gestational dietary characteristics. Evidence from the studies outlined here implies that prepartum nutrition has effects on postnatal growth and body composition, which have great significance for food

29

animal production.

More specifically, fetal skeletal muscle and adipose tissue

development may be altered by the dam’s source of dietary energy prepartum. These changes may be mediated by the somatrophin/growth system, which is important to postnatal growth and insulin sensitivity. A more in depth investigation of energy sources such as starch, fiber, and fat in prepartum diets should be conducted. The source of these caloric inputs may affect the cost of production, as well as performance and health of the dam and offspring. Positive effects on carcass characteristics, composition, and meat quality may be realized by manipulating the source of energy in diets of gestating ruminants.

30

CHAPTER 2 EFFECTS OF PREPARTUM DIETARY ENERGY SOURCE ON PRE- AND POSTPARTUM COW PERFORMANCE

ABSTRACT Mature Angus-cross beef cows (n = 147) were used to determine the effects of late gestation dietary energy source on pre- and postpartum cow performance in a complete randomized block design. Cows were adapted to diets starting at 209 ± 9 d of gestation and fed until 1 wk prior to expected calving date. Cows were fed 1 of 3 dietary energy sources at isoenergetic intakes: hay (HAY); corn (CORN); or dried distiller grains (DDGS). Cows allotted to HAY were allowed ad libitum access to round-bale grass hay and average DMI was 12.4 kg/d. Limit-fed corn and DDGS diets contained 5.3 kg wholeshelled corn or 4.1 kg DDGS, respectively, plus 2.1 kg hay, and 1.0 kg supplement to meet cow nutritional needs during late gestation. Every 21 d, BW, BCS, and ultrasound 12th rib back fat (BF) data were collected. At 210 d in gestation, jugular blood samples were collected at 0, 3, 6, and 9 h postfeeding and were analyzed for plasma glucose, insulin, non-esterified fatty acids (NEFA), and blood urea nitrogen (BUN) concentrations. Following parturition, cows were fed a common diet and managed as 1 group per location. Milk production was determined by weigh-suckle-weigh procedure on d 31, 100, and 176 postpartum. Cows fed DDGS during late gestation gained more (P

31

= 0.04) BW than cows fed HAY or CORN, however no difference in BCS change was detected (P = 0.28) among treatments. Plasma glucose concentrations were similar among treatments (P = 0.64) whereas insulin concentrations at 3 h postfeeding were greater (P = 0.002) for cows fed DDGS than those fed HAY or CORN.

Plasma BUN

concentrations were greater (P ≤ 0.02) for cows fed DDGS vs. CORN or HAY up to 6 h postfeeding.

Cows fed HAY tended (P ≤ 0.09) to have greater plasma NEFA

concentrations at 0 and 3 h postfeeding than cows fed CORN or DDGS. Birth weight was greater (P < 0.001) for calves from cows fed CORN and DDGS than for those fed HAY, but this did not result in any differences in frequency of dystocia (P = 0.21). Prepartum energy source did not affect postpartum cow performance for conception rates (P = 0.79), milk production (P ≥ 0.51) or milk composition (P ≥ 0.39). Maternal dietary energy source in late gestation did not affect pre- or postpartum cow performance, but did change plasma hormones and metabolites during gestation. Heavier birth weights in calves from cows fed CORN or DDGS indicate the alternations in maternal metabolism affected energy partitioning of nutrients to the fetus and subsequent fetal growth.

INTRODUCTION One of the major determinants of net income in a cow/calf enterprise is feed costs (Story et al., 2000), therefore, identification of economical feed sources would be advantageous. Corn can be an economical alternative to harvested or stockpiled forages and corn and can be limit-fed in late gestation diets without negative effects on cow performance (Loerch, 1996, Schoonmaker et al., 2003). With increased availability of ethanol co-products, dried distillers grains (DDGS) will become more competitively

32

priced with other protein and energy sources, however limited information has been published on effects of DDGS in limit-fed prepartum diets. Maternal energy source could impact nutrient supply of glucose and amino acids to the gravid uterus, and these are important substrates for fetal growth (Bell et al., 2005). Additionally, energy demand by the gravid uterus is greatest during the last trimester (Ferrell et al., 1976). Previously, Loerch (1996) has reported heavier birth weights in calves from cows fed a starch vs. fiber-based diet, suggesting maternal energy source when fed at isocaloric intakes impacts fetal growth. Prepartum energy intake (Perry et al., 1991; Marston et al., 1995) and protein content (Ocak et al., 2005) has resulted in increased milk production, whereas prepartum fat supplementation has resulted in no effects on milk production (Alexander et al., 2002; Banta et al., 2006). Reproductive performance has been associated negatively with nutrient restriction (Dunn and Moss, 1992) and positively with fat supplementation (Bellows et al., 2001), but other studies have reported no effects from prepartum supplementation of fat (Small et al., 2005) or DDGS (Engel et al., 2008). These studies have reported conflicting results on the impacts of prepartum nutrition on postpartum milk production and reproductive performance in cattle. Therefore, the objectives of this experiment were to determine the effects of prepartum energy source on cow prepartum performance and metabolism; postpartum milk production; and postpartum reproductive performance.

33

MATERIALS AND METHODS Animals, Experimental Design, Treatments The Agricultural Animal Care and Use Committee of The Ohio State University approved the procedures used in this experiment. Mature Angus-cross cows (n = 147) were used in a randomized complete block design experiment to determine the effects of late gestation dietary energy source on pre- and postpartum cow performance. The study was conducted at 3 branch locations of the Ohio Agricultural Research and Development Center: The Ohio State University campus (OSU), Columbus; North Appalachian Experimental Watershed (NAEW), Coshocton; and Eastern Agricultural Research Station (EARS), Belle Valley. In June 2007, cows were synchronized for timed artificial insemination (AI) to a single sire, and clean-up bulls were exposed to cows for 30 d, 3 wk after AI. Pregnancy diagnosis was conducted by transrectal ultrasound approximately 30 d after AI, and then conducted again approximately 60 d after bull removal by either transrectal ultrasound or hand palpation. Only cows confirmed by ultrasound for first AI service conception were used in the trial. The cows were blocked by location (n = 42, OSU; n = 51, NAEW; n = 54, EARS) and within location, were stratified by body weight (BW), body condition score (BCS), and cow age and were assigned to 1 of 3 pens at OSU, 1 of 3 pens at NAEW, and 1 of 9 pens at EARS. Dietary treatments were randomly assigned to pens within a location. Cows were removed from the experiment for reproductive failure, failure to calve before 300 d after first AI service, and death (Table 2.1). In November 2007, cows were adapted to diets starting at an average of 167 ± 9 d of gestation. Dietary treatments were 1 of 3 dietary energy sources; ad-libitum grass hay

34

(fiber; HAY); limit-fed corn (starch; CORN) or limit-fed corn DDGS (fiber plus fat, DDGS). In all locations, cows fed CORN and DDGS were housed in drylot pens and were provided at least 0.6 m of bunk space per cow. At EARS and OSU, cows fed HAY were housed in similar drylot pens as their counterparts; whereas, in COSH cows fed HAY were fed in a dormant 21-ha pasture, where available forage was removed by grazing prior to the initiation of the trial. Diets were formulated to meet or exceed cow nutrient requirements during late gestation (NRC, 2000) and intake of CORN and DDGS diets were limited to achieve isoenergetic intakes among dietary treatments (Table 2.2). Cows fed HAY were allowed ad libitum access to hay in round bale feeders and fed to minimize waste. Hay bales were weighed prior to feeding, but refusal was not recorded because it was impossible to accurately quantify. The hay provided was primarily orchardgrass. Cows fed HAY were provided with ad libitum access to a salt and mineral mix (29.5% trace mineralized salt, 25% dicalcium phosphate, 25% magnesium oxide, 10% limestone, 10% ground shelled corn, 0.5% ethylene diaminedihydroiodide, and 50 ppm selenium). Fifteen bales in each location were randomly selected, cored, and core samples were composited for nutrient analysis. Limit-fed CORN and DDGS diets were fed once daily and provided 5.3 kg whole shelled corn vs. 4.1 kg DDGS, plus 2.1 kg square-bale grass hay, and 1.0 kg of supplement per cow on a DM basis (Table 2.3). A 4-d adjustment period in which hay was gradually decreased was used to acclimate cows to the limit-fed diets of CORN and DDGS. Diet samples were collected every 21 d and composited for nutrient analysis.

35

Starting at 2 wk after the adaptation period, every 21 d during gestation BW, BCS (1 = emaciated; 9 = obese; Wagner et al., 1988), and ultrasound measurement of back fat (BF) between the 12th and 13th ribs were collected. The diets were adjusted if needed every 21 d during the trial to maintain similar BW gain and BCS between cows fed CORN and DDGS to cows fed HAY as well as to compensate for energy needs in cold environmental temperatures. Cows were removed from diets 1 wk prior to expected calving date, fed a common diet of grass hay until parturition; and then managed on pasture as 1 group within location until weaning. All feed samples were ground using a Wiley mill (1-mm screen; Arthur H. Thomas, Philadelphia, PA) and analyzed for DM (100° C); NDF (using sodium sulfite and heat-stable α-amalyse; Ankom200 Fiber Analyzer, Ankom Technology, Fairport, NY); CP (macro Kjeldhahl N x 6.25); fat (using ether extract method; Ankom Technology, Fairport, NY) and select macro minerals (Ca, P, and S; AOAC, 1997). Postpartum Measurements Milk production was measured at approximately 31, 100, 170 d postpartum using a modification of the weigh-suckle-weigh technique described by Boggs et al. (1980). Calves were separated from their dams for 3-h prior to the milk intake measurement. After the 3-h separation, calves were allowed to nurse their dams dry, and then were separated again for 6 h (at 31 d postpartum) or 12 h (for 100 and 170 d postpartum). After 6- or 12-h separation, the calves were weighed. Then, the calves were allowed to suckle their dams and were reweighed immediately once suckling had ceased. Milk production was assumed to be the difference between the 2 weights and milk production per day was calculated by multiplying intake by 4 for 6-h separation at 31 d postpartum

36

and by 2 for 12-h separation at 100 and 170 d postpartum. Before the weigh-suckleweigh procedure, calves were assigned randomly to 1 of 3 groups within location and started at consecutive 30 min intervals to more closely monitor the calves during suckling. During the initial 3-h separation, a milk sample (approximately 50 mL) was collected by hand from each cow and treated with bronopol and natamycin as preservatives and held at 4°C until analyzed for composition by a commercial laboratory as described by Beckman and Weiss (2005). In 2 locations (OSU and EARS), postpartum reproductive performance was measured. Postpartum anestrus was assessed by determination of percentage of cows cycling at approximately 60 d postpartum and then cows were synchronized for timed AI at approximately 80 d postpartum. Between 2 to 4 wk after first service, cows detected in estrus were AI again for a second service. Cows were exposed to clean-up bull for 28 d starting at approximately 4 wk after first service AI. Pregnancy was diagnosed by transrectal ultrasound between 30 and 35 d after timed AI to determine first service AI pregnancy rate. A second pregnancy diagnosis was performed 90 to 100 d after first AI by transrectal ultrasound to determine 2nd service AI conception rates and overall pregnancy rates. Blood Collection and Analysis At 210 d of gestation, a subset of cows (5 cows per pen at NAEW and OSU; 2 cows per pen at EARS) were randomly selected and then jugular blood samples were collected at 0, 3, 6, and 9 h after feeding CORN and DDGS diets. Blood samples from each cow were collected in 2 Vacutainer (Becton, Dickson and Co., Franklin Lakes, NJ) collection tubes with 1 containing EDTA and 1 containing 15 mg NaF and 12 mg K

37

oxaloate per tube. Blood samples were placed on ice until they were centrifuged at 3,000 x g for 20 min at 4°C. Plasma collected from tubes containing EDTA were frozen at 80°C for subsequent analysis of blood urea nitrogen (BUN), non-esterified fatty acids (NEFA), and insulin. Plasma collected from tubes containing Na fluoride were frozen at -20°C for subsequent glucose analyses. Concentrations of insulin were measured using RIA as described previously (Benson and Reynolds, 2001). The intra-assay CV was 12%. Colormetric assay was used to determine concentrations of plasma glucose (#1070 Glucose Trinder, Standbio Laboratory, Boerne, TX); plasma NEFA (Wako Chemicals USA, Richmond, VA) as described by Johnson and Peters (1993); and plasma BUN (BioAssay Systems, Hayward, CA). At 189, 210, and 231 d of gestation, the same subset of cows were used to collect jugular blood samples prior to feeding for progesterone analysis as an indication of placenta size and function. To determine percentage of cows cycling at 60 d postpartum, jugular blood samples from all cows were taken on approximately 38 and 47 d postpartum at the EARS and OSU locations to detect cows with an active corpus luteum. When either of the two blood samples had concentrations of progesterone ≥ 1 ng/mL, the cow was considered to be cycling (Perry et al., 1991). Plasma progesterone was measured from blood collected in a Vacutainer (Becton, Dickson and Co., Franklin Lakes, NJ) collection tube containing EDTA. After centrifugation at 3,000 x g for 20 min at 4°C, plasma was recovered and stored at -20°C until subsequent analysis. Progesterone concentrations were determined using a commercially available RIA kit (Coat-a-Count, Diagnostic Products Corporation, Los Angeles, CA) as described previously by Burke et al. (2003).

38

Statistical Analysis Twenty cows were removed from the trial due to various reasons (Table 2.1) and data from these cows were not used for statistical analyses. The GENMOD procedure of SAS (SAS Inst. Inc., Cary, NC) was used to analyze binomial data (dystocia, cycling, conception, and pregnancy rates). The PROC MIXED procedure of SAS was used to analyze the remaining variables. The PDIFF statement of SAS was used to separate treatment means when significant (P < 0.10). Experimental unit was pen and location was included as a random variable in all analyses. Cow measures of prepartum plasma data, postpartum milk production, and postpartum milk production were analyzed using a repeated measures model. For each analyzed variable, 5 covariance structures were compared: compound symmetric, autoregressive order one, heterogeneous autoregressive order one, spatial power, and unstructured. The covariance structure that yielded the smallest Bayesian information criterion was used for the results presented. For plasma metabolites and hormones, maternal dietary energy source, h post-feeding, and the 2-way interaction were used in the model. For postpartum variables, gestational dietary energy source, d postpartum and the 2-way interaction were tested. Simple effects within h post-feeding and d postpartum were generated by the SLICE function of SAS.

RESULTS AND DISCUSSION Prepartum cow measurements

39

The prepartum diets were initially formulated to provide similar NEm intake among treatments according to NRC (2000) for CORN and HAY diets, whereas the energy value used for DDGS was greater than reported by NRC (2000). Based on previous studies investigating DDGS inclusion levels from 10 to 64% in high-concentrate diets to beef steers, the energy value relative to corn has been reported to range from 83 to 124% with the average at 110% (Stock et al., 2000). Therefore, an energy value for DDGS of 110% of corn was used to formulate the diets and establish intake at the start of the trial. In Table 2.3, DMI and daily feed costs during late gestation are reported. Cows fed HAY consumed (includes any hay wasted) 12.4 kg of DM/d (NEm = 14.34 Mcal/d); cows fed CORN consumed 8.4 kg of DM/d (NEm = 16.05 Mcal/d.); and cows fed DDGS consumed 7.2 kg of DM/d (NEm = 14.10 Mcal/d.). Cows fed CORN had a higher energy intake during gestation than initially formulated, because the amount of corn was increased in the diet starting at 210 d of gestation in January to match BW gain of cows fed HAY, and to compensate for energy needs in cold environmental temperatures and increasing cow requirements during late gestation. However, the amount of DDGS fed to cows during late gestation was not changed at this time, because change in BW between cows fed DDGS and HAY was not great enough to justify a reduction in intake. Using average commodity prices paid during the trial, diet costs per cow were reduced 24% by feeding DDGS instead of HAY as the primary energy source during late gestation (Table 2.3). In previous studies, limit-feeding corn has been an economic alternative to hay in late gestation diets (Loerch, 1996; Schoonmaker et al., 2003). However, in those studies, corn was valued at 50% less per kg than the present study. Due to such factors as rising food costs, fuel costs, and increased ethanol production,

40

corn has increased significantly in value; thereby requiring identification of economic alternatives. In accordance with experimental objectives, initial BW, BCS and BF were not different among treatments at the start of the study (Table 2.4). The final measurements for BW, BCS and BF were collected 3 wk prior to expected calving date. There were no differences (P > 0.28) in BCS among cows fed HAY, CORN or DDGS. Cows fed DDGS gained approximately 20 kg more (P < 0.05) BW than cows fed CORN or HAY. In addition, cows fed DDGS also gained more (P ≤ 0.03) BF than cows fed HAY during late gestation. A difference of 4% in weight gain in cows fed DDGS vs. CORN or HAY indicates DDGS may have a higher energy value under these feeding conditions than calculated at the start of the trial. Therefore, DDGS could have been fed at a lesser amount to achieve the same late gestation performance as cows fed HAY or CORN. Higher inclusion levels of DDGS (30% or greater) are typically associated with reduced DMI (Leupp et al., 2009; Vander Pol et al., 2009), which has been attributed to increasing fat and sulfur content of the diet. In the present study, intakes were intentionally limited to meet cow requirements and cows readily consumed their ration. Therefore, fat and sulfur intakes did not affect intake or appear to affect cow performance. Few studies have been conducted investigating inclusion levels of 50% or greater of DDGS in beef cattle diets. Lactating beef cows fed DDGS at 55% inclusion had a smaller reduction in BW and BCS but had lower milk production than cows fed dried corn gluten feed (Shike et al., 2009), and suggests energy partitioning may have been altered by feeding DDGS. Studies in feedlot cattle have reported a similar result where higher inclusion levels of

41

DDGS in replacement of corn have been associated with more subcutaneous fat, less muscle, and reduced intramuscular fat (Reinhart et al., 2007). The current study would suggest energy content of DDGS was greater than 110% of corn and DDGS partitioned more energy to subcutaneous fat deposition. However the changes in BF were not detectable in visual BCS, and therefore, may not have practical significance. The three energy sources fed during late gestation resulted in similar (P = 0.30) plasma glucose concentrations pre- and postfeeding (Figure 2.1), whereas plasma insulin concentrations were greater (P = 0.001) 3 h postfeeding in cows fed DDGS vs. cows fed CORN or HAY (Figure 2.2). Our hypothesis was that feeding a diet high in starch (corn) would increase maternal glucose supply to the fetus due to greater propionate production during ruminal fermentation. Propionate stimulates release of insulin and is converted to glucose by the liver, which would also stimulate insulin secretion (Harmon, 1992). However, the plasma insulin and glucose results from the present study did not follow this hypothesis. In gestating (Susin et al., 1995a) and lactating ewes (Susin et al., 1995b) limit-fed high-grain diets, glucose and insulin concentrations were greater when compared to high-forage diets at similar caloric intakes. Other studies in dairy cattle have reported an increase in plasma glucose and insulin concentrations in comparing high-grain vs. forage diets (Palmquist and Conrad; 1971; Dhiman et al., 1991). Recent studies in dairy cattle investigating prepartum diets with differing energy sources but similar ME intake have observed no difference in plasma glucose concentrations (Moorby et al., 2000; Smith et al., 2008;); however, the differences in forage to concentrate ratios were smaller than for the present study.

42

Insulin secretion is also up-regulated by elevated levels of amino acids (Harmon, 1992). Dried distillers grains has a higher crude protein content with a greater proportion of undegradable intake protein (UIP) than either corn or hay (73%, 55.3%, and 36% UIP, respectively; NRC, 2000). Cows fed DDGS diets in the present study consumed 1477 g CP/d whereas cows fed HAY and CORN consumed at least 400 g less of CP per d., therefore more amino acids would be expected to be absorbed post-ruminally in cows fed DDGS diets. In agreement with the present study, undegraded intake protein (UIP) supplementation in late-gestation was observed to increase plasma insulin concentrations with increasing UIP supplementation (Sletmoen-Olson et al., 2000). In addition, Luepp et al. (2009) reported DDGS, fed at 60% inclusion in growing cattle diet, resulted in greater propionate production when compared to corn. Together greater amino acid absorption post-ruminally and ruminal propionate production could have stimulated greater insulin secretion in cows fed DDGS vs. cows fed HAY or CORN. Plasma NEFA concentrations tended to be greater (P = 0.09) for cows fed HAY and DDGS prior to feeding and tended to be greater (P = 0.08) for those fed HAY at 3 h post-feeding as compared to cows fed CORN or DDGS (Figure 2.3). Energy balance in cows is negatively correlated with plasma NEFA concentrations (Lucy et al., 1991), because NEFA can be a measure of mobilization of lipid stores.

Higher NEFA

concentrations in cows fed HAY could indicate mobilization of body fat from reserves for additional energy and this corresponds with the reduction in BCS and BF in cows fed HAY during this period. In contrast, cows fed DDGS increased BF during late gestation as compared to those fed CORN or HAY. The cows fed DDGS had greater circulating NEFA concentrations prior to feeding than those fed HAY or CORN, which may reflect

43

the greater fat content of the diet. In lactating dairy cows fed dietary fat, NEFA was almost always increased (as reviewed by Grummer and Carroll, 1991). Plasma BUN concentration (Figure 2.4) was greater (P ≤ 0.02) in cows fed DDGS at 0 and 3 h post-feeding as compared to cows fed HAY or CORN, which is to be expected, because CP content of the diet is directly related to plasma concentration of BUN (Preston et al., 1965; Hammond, 1983).

Diets were designed to provide

isoenergetic intake but not isonitrogeneous content, therefore the CP intake of the DDGS diet was over 50% greater than either HAY or CORN. In 70% concentrate beef diets similar to the present study, Leupp et al. (2009) reported inclusion of DDGS as a replacement for corn increased postruminal CP digestibility (55.6% for 0% inclusion and 67.3% for 60% inclusion of DDGS). Although CORN diets had the lowest amount of g of CP fed per day, the amount of UIP was greater than in HAY diets. Increasing UIP supplementation in gestating beef cow diets was associated with increases in plasma BUN concentration (Sletomoen-Olson et al., 2000).

This could explain the greater

plasma BUN concentration in cows fed CORN than cows fed HAY at 6 h post-feeding. In addition, cows fed HAY had free access to hay, therefore these differences could reflect when HAY was consumed compared to when CORN and DDGS diets were consumed. Progesterone is produced primarily by the corpus luteum during early to midgestation, but by approximately 90 d of gestation the placenta becomes the predominate source of progesterone in the pregnant cow. Progesterone has been associated with placental weight and birth weight in beef heifers (Villa-Godoy et al., 1990; Sullivan et al., 2009). Cow fed DDGS had greater (P = 0.02) circulating concentrations of progesterone

44

at 210 d of gestation when compared to cows fed CORN or HAY (Fig. 2.5). Diets with greater protein content (0.4 vs. 1.4 kg CP) fed to beef heifers in mid-gestation resulted in heavier birth weights; greater progesterone concentration prior to parturition; and greater placenta and cotyledonary weights (Sullivan et al., 2009). Additionally, high protein diets have been associated with increased metabolic clearance of progesterone by the liver (Parr et al., 1993). Therefore, greater circulating progesterone concentrations in cow fed DDGS could be indicative of greater placenta weight or function, which could impact fetal growth. Parturition Calf birth weight was heavier (P < 0.001) in calves from cows fed CORN and DDGS than calves from cows fed HAY (Table 2.4). Differences in birth weights among treatments were not associated with differences in gestation length (P = 0.27) or frequency of dystocia (P = 0.21) among treatments. Linear estimates have been conducted on the association of calf birth weight and dystocia with estimates for a 1.63 to 2.30% increase in dystocia for each 1 kg increase in birth weight (Hickson et al., 2006). Previous studies investigating limit-feeding corn in late gestation diets have also reported heavier birth weights but no increase in calving difficulty (Loerch, 1996; Schoonmaker et al., 2003). Increases in birth weight due to maternal dietary energy source do not appear to be associated with increased frequency of dystocia in mature cows. In agreement with previous studies, calves from cows fed CORN had heavier birth weights than calves from cows fed HAY (Loerch, 1996; Schoonmaker et al., 2003). Glucose supply to the fetus is determined by maternal glucose concentration and placental blood flow, which can alter fetal growth (Bauman et al., 2002). High-starch

45

diets can lead to increased propionate production and circulating glucose. In spite of this, in the present study maternal circulating glucose and insulin concentrations were not different between cows fed a starch vs. fiber diet. The heavier birth weights could be the effect of greater circulating BUN concentration and CP intake in cows fed DDGS than HAY, which would suggest greater maternal amino acid supply available to the placenta and fetus. Intake of CP was greater for cows fed HAY than cows fed CORN, however, these diets were similar in availability of metabolizable protein (1163 vs. 1178 g MP/d, respectively; NRC 2000). In contrast cows fed DDGS has both greater CP intake and availability of metabolizable protein (1350 g MP/d) than cows fed CORN or DDGS. Therefore, excess protein would not be a plausible explanation for the differences in birth weight between calves from cows fed CORN and HAY, but could explain the differences between calves from cows fed DGGS and those from cows fed HAY. Previous studies have demonstrated CP intake can impact fetal growth in sheep (Ocak et al., 2005) and cattle (Sullivan et al., 2009). Amino acids are major substrates for fetal growth and development (Bell et al., 2005). In addition, abundance of arginine and associated amino acids increases amount of NO synthase and thus, increases nitric oxide production, which is a vasorelaxing factor and plays a key role in regulating blood flow (Bird et al., 2003). In contrast, supplemental protein during late gestation in beef cows grazing native range did not affect birth weight (Stalker et al., 2006; Larson et al., 2009;), but differences in CP intake were smaller than the present study. Limited data have been reported on effects of feeding excess protein in gestating beef cattle diets at concentrations similar to the present study because the practice is generally expensive

46

and uncommon. Increasing availability of DDGS and use of DDGS as an energy source may warrant more research of excess protein effects in gestation diets of beef cattle. In the present study, excess CP intake with the DDGS diet could have affected energy metabolism, protein metabolism, or both. Similarly, the resultant effects on the fetus could not be distinguished. Energy status of the dam is critical to fetal growth by influencing nutrient uptake by the gravid uterus, which is greatest during the last trimester (Ferrell et al., 1976). Late-gestation maternal energy restriction, which results in reduced BW and BCS, is associated with lower birth weight (Corah et al., 1975; Freetly et al., 2000), but when cows are fed to maintain BW and BCS with adequate energy in late-gestation, birth weight was not affected independent of previous plane of nutrition during mid-gestation (Morrison et al., 1999; Freetly et al., 2000). In contrast, cows in the current study fed CORN or HAY maintained similar BW and BCS in late gestation, but birth weight was altered, indicating maternal dietary energy source may explain the difference in birth weight rather than energy status of the dam. Limit-feeding high-concentrate diets have been shown to decrease maintenance requirements in growing lambs by reducing visceral organ mass (Fluharty and McClure, 1997; Fluharty et al., 1999). Additionally, gut energy expenditure is more related to changes in mass relative to ME intake than in changes of viscera metabolism (McLeod and Baldwin, 2000). Therefore, limit-feeding corn to gestating cows may allow more energy to be partitioned to the fetus instead of maintaining maternal tissues.

This

reduction in maintenance requirements could partially explain greater fetal growth in calves from dams fed CORN or DDGS.

More research is warranted to determine

47

metabolic changes in the dam due to dietary energy source that affect nutrient supply to the fetus, especially when feeding high-starch diets. Postpartum Cow Measurements No prepartum dam energy source by d postpartum interactions were detected (P ≥ 0.15) for any postpartum variables and means for treatments are presented in Table 2.5. Prepartum energy source did not affect postpartum estimated milk production (P ≥ 0.41) or composition. Previous studies have reported energy restriction (70%) late gestation, resulted in reduced milk production was reduced (Corah et al., 1975). In addition, ewes fed diets high in protein prepartum have resulted in decrease colostrum and milk production (Ocak et al., 2005), whereas, supplemental protein had no effect on milk production and composition in beef cattle (Alexander et al., 2002; Banta et al., 2006). The present study would indicate when cows are fed adequately in late gestation, energy source does not alter subsequent milk production. No effects were detected (P ≥ 0.66) in postpartum cow reproduction performance due to cow prepartum energy source (Table 2.6). The impacts of prepartum nutrition on postpartum reproduction performance in beef cattle have not been well elucidated especially in regards to energy source, and conflicting results have reported in prepartum fat and protein supplementation on postpartum reproduction in beef cows. Bellows et al. (2001) reported increased pregnancy rates with prepartum fat supplementation, whereas other studies have reported no difference in duration of postpartum anestrus or first service AI conception rates with prepartum fat supplementation (Alexander et al., 2000; Small et al., 2004). Supplementing protein to cow on native range in late gestation did not affect postpartum pregnancy rates (Stalker et al., 2006; Larson et al., 2009), whereas

48

supplemental UIP during late gestation did improve overall pregnancy rates in beef heifers (Engel et. al., 2008). Morrison et al. (1999) reported prepartum changes in body energy reserves did not influence reproductive performance as long as cows calved with moderate BCS. Cows in the present study were in adequate body condition prior to breeding (BCS = 5.3 ± 0.4), which was similar to their body condition 3 wk prior to parturition. This indicates the cows were in an adequate plane of nutrition, thereby, reproductive performance was not influenced by prepartum energy source. In conclusion, prepartum dietary energy source was not associated with detrimental effects on pre- or postpartum cow performance, however DDGS as a prepartum dietary energy source can reduce daily feed costs during gestation. Differences in partitioning of energy and changes in plasma metabolites could indicate differences in maternal metabolism in late gestation due to maternal dietary energy source. These changes could subsequently affect fetal growth, as evidenced by heavier birth weights in progeny from cows fed DDGS or CORN during late gestation vs. those fed HAY. More research is warranted to determine effects of various energy sources fed to cows during late gestation on the maternal nutrient supply to the fetus.

LITERATURE CITED Alexander, B. M., B. W. Hess, D. L. Hixon, B. L. Garrett, D. C. Rule, M. McFarland, J. D. Bottger, D. D. Simms, and G. E. Moss. 2002. Influence of prepartum fat supplementation on subsequent beef cow reproduction and calf performance. Prof. Anim. Sci. 18:351-357. AOAC. 1997. Official Methods of Analysis. 16th ed. Assoc. Offic. Anal. Chem., Arlington, VA.

49

Banta, J. P., D. L. Lalman, F. N. Owens, c. R. Krehbiel, and R. P. Wettemann. 2006. Effects of interval-feeding whole sunflower seeds during mid to late gestation on performance of beef cows and their progeny. J. Anim. Sci. 84:2410-2417. Bauman, M. U., S. Deborde, and N. P. Illsley. 2002. Placental glucose transfer and fetal growth. Endocrine. 19:13-22 Beckman, J. L., and W. P. Weiss. 2005. Nutrient digestibility of diets with different fiber to starch ratios when fed to lactating dairy cows. J. Dairy. Sci. 88:10151023. Bell, A. W., P. L. Greenwood, and R. A. Ehrhardt. 2005. Regulation of metabolism and growth during prenatal growth. In: D. G. Burrin and H. J. Mersmann (ed.) Biology of Metabolism in Growing Animals. Elsevier Limited, Edinburgh, U.K. Bellows, R. A., E. E. Grings, D. D. Simms, T. W. Geary and J. W. Bergman. 2001. Effects of feeding supplemental fat during gestation to first-calf beef heifers. Prof. Anim. Sci. 17:81-89. Benson, J. A., and C. K. Reynolds. 2001. Effects of abomasal infusion of long-chain fatty acids on splanchnic metabolism of pancreatic and gut hormones in lactating dairy cows. J. Dairy Sci. 84:1488-1500. Boggs, D. L., E. F. Smith, and R. R. Schalles, B. E. Brent, L. R. Corah, and R. J. Pruitt. 1980. Effect of milk and forage intake on calf performance. J. Anim. Sci. 51:550-553. Burke, C. R., M. L. Mussard, C. L. Gasser, D. E. Grum, and M. L. Day. 2003. Estradiol benzoate delays new follicular wave emergence in a dose-dependent manner after ablation of the dominant ovarian follicle in cattle. Theriogenology 60:647–658. Corah, L.R., T. G., Dunn, and C. C. Kaltenbach. 1975. Influences of prepartum nutrition on the reproductive performance of beef females and the performance of their progeny. J. Anim. Sci. 41:819-824. Dhiman, T.R., J. Kleinmans, N. J. Tessmann, H. D. Radloff, P. van Evert, and L. D. Satter. 1991. Effect of Dietary Forage:Grain Ratio on Blood Constituents in Dairy Cows. J Dairy Sci. 74: 2691-2695. Dunn, T. G. and G. E. Moss. 1992. Effects of nutrient deficiencies and excesses on reproductive efficiency of livestock. J. Anim. Sci. 70: 1580-1593. Engel, C. L., H. H. Patterson, and G. A. Perry. 2008. Effect of dried corn distillers grains plus solubles compared with soybean hulls, in late gestation diets, on animal and reproductive performance. J. Anim. Sci. 86:1697-1708.

50

Fluharty, F. L., and K. E. McClure. 1997. Effects of dietary energy intake and protein concentration on performance and visceral organ mass in lambs. J. Anim. Sci. 75:604-610. Fluharty, F. L., K. E. McClure, M. B. Solomon, D. D. Clevenger, and G. D. Lowe. 1999. Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism. J. Anim. Sci. 77:816-823. Ferrell, C. L., W. N. Garrett, N. Hinman, and G. Gritching. 1976. Energy utilization by pregnant and non-pregnant heifers. J. Anim. Sci. 42:937-950. Freetly, H. C., and C. L. Ferrell. 2000. Net flux of nonesterified fatty acids, cholestrol, triacyglycerol, and glycerol across the portal-drained viscera and liver of pregnant ewes. J. Anim. Sci. 73:1380-1388. Freetly, H. C., C. L. Ferrell, and T. G. Jenkins. 2000. Timing of realimentation of mature cows that were feed-restricted during pregnancy influences calf birth weights and growth and rates. Grummer, R. R., and D. J. Carroll. 1991. Effects of dietary fat on metabolic disorders and reproductive performance of dairy cattle. J. Anim. Sci. 69:3838-3852. Harmon, D. L. 1992. Impact of nutrition on pancreatic exocrine and endocrine secretion in ruminants: A review. J. Anim. Sci. 70:1290-1301. Hammond, A. C., 1983. The use of blood urea nitrogen concentration as an indicator of protein status in cattle. Bovine Pract. 18:114-118. Hickson, R. E., S. T. Morris, P. R. Kenyon, and N. Lopez-Villalobos. 2006. Dystocia in beef heifers: A review of genetic and nutritional influences. New Zealand Vet. J. 54:256-264. Johnson, M. M., and J. P. Peters. 1993. Technical note: An improved method to quantify non-esterified fatty acids in bovine plasma. J. Anim. Sci. 71:753-756. Larson, D. M., J. L. Martin, D. C. Adams, and R. N. Funston. 2009. Winter grazing system and supplementation during late gestation influence performance of beef cows and steer progeny. J. Anim. Sci. 87:1147-1155. Loerch, S. C. 1996. Limit-feeding corn as an alternative to hay for gestating beef cows. J. Anim. Sci. 74:1211-1216. Luepp, J. L., G. P. Lardy, K. K. Karges, M. L. Gibson, and J. S. Caton. 2009. Effects of increasing level of corn distillers dried grains with solubles on intake, digestion,

51

and ruminal fermentation in steers fed seventy percent concentrate diets. J. Anim. Sci. 87:2906-2912. Lucy, M. C., C. R. Staples, F. M. Michel, and W. W. Thatcher. 1991. Energy balance and size and number of ovarian follicles detected by ultrasonography in early postpartum dairy cows. J. Dairy Sci. 74:473-482. Martson, T. T., K. S. Lusby, R. P. Wettemann, and H. T. Purvis. 1995. Effects of feeding energy or protein supplements before or after calving on performance of spring-calving cows grazing native range. J. Anim. Sci. 73:657-664. McLeod, K. R. and R. L. Baldwin, VI. 2000. Effects of diet forage: concentrate ratio and metabolizable energy intake on visceral organ growth and in vitro oxidative capacity of gut tissue in sheep. J. Anim. Sci. 78:760-770. Moorby, J. M., R. J. Dewhurst, J. K. S. Tweed, M. S. Dhanoa, and N. F. G. Beck. 2000. Effects of altering energy and protein supply to dairy cows during the dry period. 2. Metabolic and hormonal responses. J. Dairy Sci. 83:1795-1805. Morrison, D. Gl., J. C. Spitzer, and J. L. Perkins. 1999. Influence of prepartum body condition score change on reproductive in multiparious beef cows calving in moderate body condition. J. Anim. Sci. 77:1048-1054. Murphy, T. A., S. C. Loerch, B. A. Dehority. 1994. The influences of restricted feeding on site and extent of digestion and flow of nitrogenous compounds to the duodenum in steers. J. Anim. Sci. 72:2487-2496. NRC. 2000. Nutrient requirements of beef cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC. Ocak, N., M. A. Cam, and M. Kuran. 2005. The effect of high dietary protein levels during late gestation on colostrum yield and lamb survival rate in singletonbearing ewes. Sm. Rumin. Res. 56:89-94. Palmquist, D. L. and H. R. Conrad. 1971. Origin of Plasma Fatty Acids in Lactating Cows Fed High Grain or High Fat Diets J Dairy Sci. 54: 1025-103 Parr RA, Davis IF, Miles MA, Squires TJ. Liver blood flow and metabolic clearance rate of progesterone in sheep. Res Vet Sci 1993;55:311–6. Perry, R. D., L. R. Corah, G. H. Kiracofe, J. S. Stevenson, and W. E. Beal. 1991. Endocrine changes and ultrasonography of ovaries in suckled beef cows during resumption of postpartum estrous cycles. J. Anim. Sci. 69:2548-2555.

52

Preston, R. L., D. D. Schnakenberg, and W. H. Pfander. 1965. Protein utilization in ruminants. I. Blood urea nitrogen as affected by protein intake. J. Nutr. 86:281288. Reinhardt, C. D., A. DiConstanzo, and G. Milliken. 2007. Distiller's by-products alter carcass fat distribution of feedlot cattle. J. Anim. Sci. 85(Suppl. 2):132. (Abstr.). Schoonmaker, J. P., S. C. Loerch, J. E. Rossi, and M. L. Borger. 2003. Stockpiled forage or limit-fed corn as alternatives to hay for gestating and lactating beef cows. J. Anim. Sci. 81:1099-1105. Shell, T. M., R. J. Early, J. R. Carpenter, and B. A. Buckley. 1995. Prepartum nutrition and solar radiation in beef cattle: II. Residual effects on postpartum milk yield, immunoglobulin, and calf growth. J. Anim. Sci. 73:1303-1309. Shike, D. W., D. B. Faulkner, D. F. Parrett, and W. J. Sexton. 2009. Influences of corn co-products in limit-fed rations on cow performance, lactation, nutrient output, and subsequent reproduction. Prof. Anim. Sci. 25:132-138. Short, R. E., R. A. Bellows, R. B. Staigmiller, J. G. Berardinelli, and E. E. Custer. 1990. Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle. J. Anim. Sci. 68: 799-816. Sletmoen-Olson, K. E., J. S. Caton, K. C. Olson, D. A. Redmer, J. D. Kirsch, and L. P. Reynolds. 2000. Undegraded intake protein supplementation: II. Effects on plasma hormone and metabolite concentrations in periparturient beef cows fed low-quality hay during gestation and lactation. J. Anim. Sci. 78:456-463. Small, W. T., S I. Paisley, B. W. Hess, S. L. Lake, E. J. Scholljegerdes, T. A. Reed, E. L. Belden, and S. Bartle. 2004. Supplemental fat in limit-fed high grain prepartum diets of beef cows: Effects on cow weight gain, reproduction, and calf health, immunity, and performance. West. Sec. Am. Soc. Anim. Sci. 55: 45-52. Smith, K. L., M. R. Waldron, L. C. Ruzzi, J. K. Drackley, M. T. Scoca, and T. R. Overton. 2008. Metabolism of dairy cows as affected by prepartum dietary carbohydrate source and supplementation with chromium throughout the periparturient period. J. Dairy Sci. 91:2011-2020. Stock, R. A., J. M. Lewis, T. J. Klopfenstein, and C. T. Milton. 2000. Review of new information on the use of wet and dry milling feed by-products in feedlot diets. 77: v-12. Stalker, L. A., D. C. Adams, T. J. Klopfenstein, D. M. Feuz, and R. N. Funston. 2006. Effects of pre- and post-partum nutrition on reproduction in spring calving cows and calf feedlot performance. J. Anim. Sci. 84:2582-2589.

53

Story, C. E., R. J. Rasby, R. T. Clark, and C. T. Milton. 2000. Age of calf at weaning of spring-calving beef cows and the effect on cow and calf performance and production economics. J. Anim. Sci. 78:1403-1413. Susin, I., S. C. Loerch, and K. E. McClure. 1995a. Effects of feeding a high-grain diet at a restricted intake on lactation performance and rebreeding of ewes. J. Anim. Sci. 73:3199-3205. Susin, I., S. C., Loerch, K. E. McClure, and M. L. Day. 1995b. Effects of limit feeding a high-grain diet on puberty and reproductive performance of ewes. J. Anim. Sci. 73:3206-3215. Sullivan, T. M., G. C. Micke, R. S. Magalhaes, G. B. Martin, C. R. Wallace, J. A. Green and V. E. A. Perry. 2009. Dietary protein during gestation affects circulating indicators of placental function and fetal development in heifers. Placenta. 30:348-354. Wagner, J. J., K. S. Lusby, J. W. Oltjen, J. Rakestraw, R. P. Wettemann, and L. E. Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizable energy requirement during winter. J. Anim. Sci. 66:603-612. Vander Pol, K. J., J. K. Leube, G. I. Crawford, G. E. Erickson, and T. J. Klopfenstein. 2009. Performance and digestibility characteristics of finishing diets containing distillers grains, composites of corn processing coproducts, or supplemental corn oil. J. Anim. Sci. 87:639-652.

54

Table 2.1. Reasons for cows being removed from the trial. Item Initial cows, n Prepartum mortality, n2

HAY 49 --

Treatment1 CORN 49 1

Non-first service AI, n3

--

2

1

Pre-term abortions, n

--

2

2

DDGS 49 2

Birth defects, n4 2 1 -5 Calf mortality, n 1 2 2 Twins, n -1 -6 Postpartum mortality, n --1 Total removed, n 3 9 8 1 HAY = hay; CORN = limit-fed corn; DDGS = limit-fed dried distillers grains. 2 Cow died to causes determined not to be associated with treatments. 3 Cows were removed if calving did not occur within 300 d of 1st service AI date. 4 Calves were born with birth defects determined not be associated with treatments. 5 Calves were dead at birth with no dystocia observed. 6 Cow died of respiratory disease postpartum.

55

Table 2.2. Late gestation diets and nutrient composition Treatment1 HAY2

CORN

DDGS

Ingredient ------------------------- % DM basis ------------------Grass hay 100.00 27.50 30.50 Whole shelled corn -60.00 -DDGS --66.516 Ground corn -3.331 -Soybean meal -5.83 -Limestone -0.97 1.53 Dicalcium phosphate -0.54 -Urea -0.52 -3 Trace mineral salt -0.40 0.44 Animal and vegetable fat -0.34 0.38 Potassium chloride -0.26 0.29 Magnesium oxide -0.16 0.18 4 Mg and K sulfate -0.07 0.08 Selenium, 201 mg/g -0.04 0.04 Vitamin A, 30,000 IU/g -0.013 0.015 Vitamin D, 3,000 IU/g -0.013 0.015 5 Monensin -0.013 0.014 Analyzed nutrient content CP, % 8.21 11.37 20.52 NDF, % 68.10 24.17 40.08 ADF, % 41.10 12.99 24.42 Ether extract, % 2.00 3.87 8.64 Ca, % 0.20 0.65 0.73 P, % 0.47 0.31 0.53 S, % 0.18 0.16 0.29 1 HAY = hay; CORN = limit-fed corn; DDGS = limit-fed dried distillers grains. 2 Cows were provided ad libitum access to a trace-mineral salt mix (29.5% trace mineralized salt, 25% dicalcium phosphate, 25% magnesium oxide, 10% limestone, 10% ground corn, 0.5% ethylene diaminedihydroiodide, and 50 ppm selenium) 3 Contained 98% NaCl, 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% I, and 0.007% Co. 4 Magnesium sulfate and potassium sulfate. Contained 22% S, 18% K, 11% Mg. 5 Provided 28 mg of monensin/kg of dietary DM. 56

Table 2.3. Nutrient intake and daily feed cost during gestation Item DMI, kg/d Hay, kg/d

HAY 12.4 12.4

Treatment1 CORN 8.4 2.1

DDGS 7.2 2.1

Corn, kg/d

--

5.3

--

DDGS, kg/d

--

--

4.1

Supplement, kg/d NEm intake, Mcal/d3 CP intake, g/d Crude fat intake, g/d Daily feed costs, $/cow2 Total feed costs, $/cow

-14.14 1018 248 1.36 159.59

1

1.0 16.05 955 325 1.46 171.02

1.0 14.34 1477 622 1.04 121.48

HAY = hay; CORN = limit-fed corn; DDGS = limit-fed dried distillers grains. Calculated with the following prices on an as-fed basis: corn = $0.149/kg ($3.80/bu); hay = $0.110/kg ($100/ton); DDGS = $0.143/kg ($130/ton); CORN supplement = $0.441/kg ($400/ton); and DDGS supplement = $0.221/kg ($200/ton). 3 Calcuated from NRC (2000) except for DDGS. Assumed DDGS was 110% energy value of corn (as reviewed by Stock et al., 1999). 2

57

Table 2.4. Effects of prepartum energy source on gestation cow performance Treatment1 CORN 44(5)

Item HAY DDGS SEM P-value Cows (pens) 49(5) 44(5) BW, kg Initial 608.5 605.7 605.6 4.4 0.77 b b a Final 657.4 654.2 676.2 5.7 0.04 b b a Change 51.1 47.1 71.1 6.9 0.05 b b a ADG, kg/d 0.52 0.48 0.72 0.07 0.05 BCS2 Initial 5.4 5.4 5.3 0.1 0.69 Final 5.1 5.4 5.6 0.3 0.33 Change -0.30 0.06 0.27 0.20 0.28 Backfat3, cm Initial 0.46 0.54 0.50 0.07 0.57 Final 0.46 0.60 0.60 0.06 0.16 b ab a Change 0.003 0.061 0.107 0.023 0.03 Gestation length, d 279.4 281.1 280.4 0.9 0.27 b a a Calf birth wt., kg 38.8 43.1 41.3 1.6