Influence of fish oil supplementation on growth and immune system characteristics of cattle1 T. J. Wistuba2, E. B. Kegley3, J. K. Apple, and M. E. Davis Department of Animal Science, University of Arkansas, Fayetteville 72701
ABSTRACT: A study was conducted to determine the effects of supplemental fish oil on growth performance and immune system characteristics of beef calves. The grazing phase (78 d) used 48 yearling crossbred steers (231 ± 22 kg initial BW) grazing 0.45-ha mixed-grass pastures (four per treatment) supplemented with 1.82 kg/d (as-fed basis) of the diets. Diets consisted of 1) corn-based supplement; 2) corn-based supplement with 1.5% (as-fed basis) fish oil; 3) wheat midd-based supplement; and 4) wheat midd-based supplement with 1.5% fish oil. On d 78, all calves were bled by jugular venipuncture, and blastogenic response of peripheral blood lymphocytes to phytohemagglutinin, concanavalin A, and pokeweed mitogen was measured. Fish oil supplementation negatively affected ADG with the corn-based supplement, but it had no effect when added to the wheat midd-based supplement (base-supplement × fish oil interaction; P < 0.03). Isolated lymphocytes from
calves fed the corn-based supplement with fish oil had a greater response to stimulation with concanavalin A than did lymphocytes from calves fed the corn-based supplement alone, but there was no effect of fish oil addition to the wheat midd-based supplement (basesupplement × fish oil interaction; P < 0.01). During the growing phase, the 48 steers (352 ± 32 kg initial BW) from the grazing phase were moved to drylot pens and were stratified by BW and previous dietary treatment (three calves per pen; eight pens per dietary treatment) for a 56-d growing trial. Dietary treatments consisted of 1) control, and 2) the control diet with 3% (as-fed basis) fish oil. Calves supplemented with fish oil had decreased ADG, ADFI, and G:F (P ≤ 0.02) compared with controls. Fish oil supplementation during the grazing phase modulated the immune system; however, the decreased growth performance associated with fish oil in both trials may limit its practical use as an immune stimulant.
Key Words: Cattle, Dietary Fat, Fish Oil, Immune Response 2005 American Society of Animal Science. All rights reserved.
Introduction In the human diet, fish has been the traditional source of eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6; Henderson and Toucher, 1987), and intake of these highly unsaturated n-3 fatty acids is estimated to be 0.1 to 0.2 g/d (Kris-Etherton et al., 2000). Recently, the dietary recommendation for these fatty acids was increased from 0.15 to 0.65 g/d (KrisEtherton et al., 2000). To achieve this fourfold increase in consumption, consumers will either have to adjust their diets, or the nutrient content of certain foodstuffs
1
The authors thank Omega Protein (Houston, TX) for the donation of the Menhaden fish oil, and P. Hornsby, J. Sligar, and G. Carte for expert assistance in caring for the cattle. 2 Current address: Morehead State Univ., Morehead, KY 40351. 3 Correspondence: B114 AFLS Bldg. (phone: 479-575-3050; fax: 479-575-5756; e-mail:
[email protected]). Received July 8, 2004. Accepted January 10, 2005.
J. Anim. Sci. 2005. 83:1097–1101
will need to be changed. Recent research (Ponnampalam et al., 2001) has indicated that the fatty acid composition of ruminant animals can be manipulated to contain more n-3 fatty acids. Therefore, beef is a product that potentially could be modified to meet this consumer need. Currently, fish oil is not widely used by the cattle industry because there are less expensive fat sources. Although fish oil has not been extensively investigated, the effect of feeding other fats to ruminants has been studied. Typically, added dietary fat is limited to less than 5% of the diet to minimize negative effects on ruminal digestion (Byers and Schelling, 1988). In the rumen, most triglycerides are broken down and the fatty acids are hydrogenated; however, some research indicates that long-chain n-3 fatty acids in ruminant diets may escape ruminal degradation and modify the fatty acid composition of meat and milk (Ashes et al., 1992). Nonetheless, feeding diets that alter the fatty acid content of meat could affect other aspects of beef production. Nutritional status has a profound effect on immune function, and supplements provided for
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one physiological purpose, such as muscle lipid composition, may also have physiological effects that influence immune activity (Wan et al., 1989). The objective of this study was to determine the effects of dietary fish oil addition on growth performance, and carcass and immune system characteristics of cattle.
Materials and Methods Animals All studies reported were conducted in compliance with procedures approved by the University of Arkansas Animal Care and Use Committee. In the grazing phase, 48 Angus crossbred steers (231 ± 22 kg initial BW) from the same maternal herd were obtained from the University of Arkansas Livestock and Forestry Branch Station in Batesville. Steers were shipped to the University of Arkansas Stocker and Receiving Unit before the start of the study. They were vaccinated for protection against infectious bovine rhinotracheitis, bovine viral diarrhea, parainfluenza-3, bovine respiratory syncitial virus, Haemophilus somnus, Pasteurella, and Clostridia (Cattle Master-4, Bar Somnus 2P, and Alpha-7, respectively; Pfizer, Exton, PA) and were treated for internal and external parasites (Ivomec, Merck & Co., Inc., Whitehouse Station, NJ). Steers were individually weighed, blocked by BW (four blocks), and assigned randomly to pens on May 18, 2000. There were three steers in each of the 16 pens, for a total of 12 animals per treatment. Pens were 0.45-ha mixed-grass (bermudagrass and dallisgrass) pastures. Supplements were fed at a rate of 1.82 kg/ d (as-fed basis). Treatment supplements (Table 1) consisted of 1) corn-based supplement; 2) corn-based supplement with 1.5% (as-fed basis) fish oil; 3) wheat midd-based supplement; and 4) wheat midd-based supplement with 1.5% fish oil. Full weights of the steers were taken on two consecutive days at the start (d 0) and end (d 78) of the grazing trial. Interim weights were taken on d 14, 28, 42, and 56, and steers were observed daily for signs of bovine respiratory disease. During the growing phase, the 48 crossbred steers (352 ± 32 kg initial BW) from the grazing phase were stratified by previous dietary treatment, blocked by BW, and moved to 3.7 m × 29.3 m pens. Three steers were maintained in these pens with covered bunks and bunk aprons, with a total of eight pens per dietary treatment. Dietary treatments (Table 2) consisted of 1) control, and 2) the control diet with 3% fish oil replacing a portion of the corn. Steers were fed their assigned diets for 56 d, and feed was offered once daily at approximately 0800. Bunks were observed immediately before feeding, and a quantity of feed was offered that allowed for ad libitum intake with minimal orts. Feed for the pens was weighed out immediately following bunk observations on a scale with 0.1-kg readability. Steers were individually weighed on two consecutive days at the start (d 0) and end (d 56) of the growing trial, and an interim weight was taken on d 28.
Table 1. Ingredient (as-fed basis) and nutrient compositions (% DM basis) of supplements fed during the grazing phase Item
Corn
Corn + oil
Wheat midds
Wheat midds + oil
Ingredient Corn Wheat midds Cane molasses Cottonseed hulls Soybean meal Dicalcium phosphate Limestone Salt Fish oil Vitamin premixa Trace mineral premixb
46.95 — 2 27 21 0.25 1.5 1 — 0.15 0.15
42.94 — 2 29 21.5 0.26 1.5 1 1.5 0.15 0.15
29.2 60.5 2 — 3.5 — 3.5 1 — 0.15 0.15
22.7 65.75 2 — 3.25 — 3.5 1 1.5 0.15 0.15
Nutrient DM CP Fatc NEm, Mcal/kgc NEg, Mcal/kgc
88.2 15.8 2.66 1.84 1.09
88.4 15.8 4.13 1.80 1.05
88.4 15.7 4.26 1.79 1.11
88.7 15.9 5.73 1.79 1.11
a Premix supplied per kilogram of supplement: 495 IU of vitamin A; 165 IU of vitamin D3; and 0.33 IU vitamin E. b Premix supplied per kilogram of supplement: 16 mg of Zn as ZnSO4; 4 mg of Cu as CuSO4; 0.1 mg of Se as Na2SeO3; 0.6 mg of I as CaIO4; and 0.4 mg of Co as CoCO3. c Values calculated with the Oklahoma State Univ. Ration Calculator 1999 (as-fed version) software (www.ansi.okstate.edu/software/ OSUNRCAF.xls).
Diets The diets were mixed at approximately monthly intervals for the grazing phase and at weekly intervals for the growing phase. Menhaden fish oil (Omega Protein, Houston, TX) for the diets was delivered on approximately monthly intervals. Grazing supplements were calculated to be isonitrogenous and isocaloric, whereas growing diets were balanced to be isonitrogenous (NRC, 1996). Feed and pasture samples were taken on weigh days, placed in a drying oven, and analyzed, using the procedures of the AOAC (1990), to quantify DM and CP (procedure no. 990.03). During the grazing phase, pasture samples averaged 16.7% CP (DM basis).
Blood Sample Collection and Lymphocyte Blastogenic Response Assays On d 63 of the grazing phase, 24 calves (six steers per dietary treatment; two per pen from the two lightest weight blocks and one per pen from the two heaviest weight blocks were selected randomly) were bled by jugular venipuncture. Blood was collected into two 10mL vacuum tubes containing K3 EDTA (Vacutainer 366457, Becton Dickinson, Franklin Lakes, NJ) for blastogenic response of peripheral lymphocytes. Blastogenic response of peripheral lymphocytes to phytohemagglutinin (PHA; Sigma Chemical Co., St. Louis, MO), concanavalin A (CONA; Sigma Chemical Co.),
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Table 2. Ingredient (as-fed basis) and nutrient compositions (DM basis) of experimental diets fed during the growing phase Item
Control
Fish oil %
Ingredient Corn, cracked Cottonseed hulls Soybean meal Cane molasses Dicalcium phosphate Limestone Salt Fish oil Rumensin premixa Vitamin premixb Trace mineral premixc
64.7 20 11.2 2 0.4 0.85 0.15 0 0.4 0.15 0.15
61.7 20 11.2 2 0.4 0.85 0.15 3 0.4 0.15 0.15
Nutrient DM CP ADF NDF Fat NEm, Mcal/kgd NEg, Mcal/kgd
88.5 13.2 16.1 22.6 3.19 1.96 1.19
88.9 12.9 15.5 21.9 6.39 2.04 1.26
a Rumensin 80 (Elanco Anim. Health, Greenfield, IN) premix supplied 20 mg of monensin/kg of diet (as-fed basis). b Premix supplied per kilogram of diet: 495 IU of vitamin A; 165 IU of vitamin D3; and 0.33 IU vitamin E. c Premix supplied per kilogram of diet: 20 mg of Zn as ZnO; 10 mg of Mn as MnO; 8 mg of Cu as CuSO4; 0.10 mg of Se as Na2SeO3; and 0.10 mg of Co as CoCO3. d Values calculated with the Oklahoma State Univ. Ration Calculator 1999 (as-fed version) software (www.ansi.okstate.edu/software/ OSUNRCAF.xls).
and pokeweed mitogen (PWM; Sigma Chemical Co.) was measured using [3H]thymidine as described by Kegley and Spears (1995). Triplicate cultures from each calf with each mitogen were supplemented with 25 µL of fetal bovine serum, using the following concentrations of mitogens: 25 µg/mL of CONA, 40 µg/mL of PHA, and 15 µg/mL of PWM.
Statistical Analyses Body weights, ADG, ADFI, G:F, and lymphocyte blastogenesis data were analyzed using the GLM pro-
cedure of SAS (SAS Inst., Inc., Cary, NC). Pen was used as the experimental unit for performance and immune characteristics. The model for the grazing phase included block and treatment. Orthogonal contrasts were used to compare the base supplement × fish oil interaction. If a base supplement × fish oil interaction was detected (P < 0.10), the PDIFF option in SAS was used to separate least squares means. The model for the growing phase included block and dietary treatment.
Results and Discussion Growth Performance During d 29 to 42 and d 0 to 78 of the grazing phase, fish oil supplementation had a negative effect on ADG (Table 3) when added to the corn-based supplement, but no effect when added to the wheat midd-based supplement (base-supplement × fish oil interaction; P < 0.03). This negative association could have been due to decreased overall fiber digestibility associated with added starch and oil. Brokaw et al. (2001) reported that feeding corn-based supplements at 0.345% of BW had no effect on OM intake, although it decreased microbial N flow and efficiency, and postruminal N disappearance compared with calves that had not been supplemented. Hess et al. (1996) reported that steers supplemented with corn at 0.34% of BW outperformed calves that were fed a wheat bran supplement at a rate of 0.34 and 0.48% of BW. These authors also reported that supplemented steers consumed less forage and total OM than the group that received no supplement. The negative association between grain feeding and forage intake might have been exacerbated by the added fat and might have been the cause of the decreased performance in the current trial, which used a higher supplementation level. Vanzant et al. (1990) reported that supplementing beef cattle with cracked corn at 0.35% of BW did not affect forage utilization by cattle grazing summer pasture; however, supplemental whole corn at 0.40% of BW decreased forage digestibility and intake in steers grazing summer
Table 3. Effect of fish oil supplementation on growth performance of cattle grazing mixedgrass pastures Corn + oil
Wheat midds
Wheat midds + oil
Item
Corn
No. of pens ADG, kg d 0 to 14a d 15 to 28 d 29 to 42b d 43 to 56 d 57 to 78a d 0 to 78ab
4
4
4
4
1.8 1.4 1.86x 0.7 1.3 1.39x
1.5 1.5 1.28y 0.6 1.2 1.20z
1.7 1.5 1.33y 0.6 1.3 1.29y
1.5 1.4 1.46y 0.6 1.2 1.23yz
Effect of fish oil addition, P < 0.05. Base-supplement × fish oil interaction, P < 0.05. Within a row, means that do not have a common superscript letter differ, P < 0.06.
a b
x,y,z
SE
0.06 0.12 0.13 0.14 0.04 0.02
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Table 4. Influence of fish oil supplementation on average daily gain, average daily feed intake, and gain to feed in the growing phase Item
Control
Fish oil
SE
P-value
No. of pens d 0 to 28 ADG, kg ADFI, kga G:Fa
8
8
1.1 9.5 0.120
0.6 8.9 0.073
0.09 0.10 0.0099
0.01 0.01 0.02
d 0 to 56 ADG, kg ADFI, kga G:Fa
1.6 11.3 0.146
1.1 9.0 0.124
0.05 0.16 0.0050
0.01 0.01 0.02
a
As-fed basis.
short-grass prairie rangeland (Pordomingo et al., 1991). During the growing phase, ADFI was decreased (P < 0.01) at 28 d and for the entire 56-d study by dietary supplementation of fish oil (Table 4). Previous research with high-concentrate diets indicated that feed intake can decrease when diets contain over 8% fat because of adverse effects of fat, particularly polyunsaturated fat, on ruminal microbial populations (Rule et al., 1989). However, Wonsil et al. (1994) reported that a diet containing 3% added oil (1.5% fish oil and 1.5% stearic acid) and 7.1% total fat, had no effect on apparent total-tract digestibility of DM, ADF, OM, or N. In the current trial, dietary fat level was increased to 6.4% with the addition of fish oil. Therefore, the decrease in intake was most likely a result of several factors such as palatability, energy density of the diet, and total fat. Scollan et al. (2001) reported that feeding cattle a diet (60:40 forage:concentrate; DM basis) containing 6% total fat in the diet with 2% from fish oil did not decrease feed intake. However, Whitlock et al. (2002) reported that the addition of 2% fish oil to lactating dairy cow diets decreased feed intake, and Wonsil et al. (1994) reported that the addition of 1.5% fish oil and 1.5% stearic acid to the diet of lactating dairy cows decreased intake by 3.2 kg/d. In the growing phase, ADG also was decreased (P < 0.01) from d 0 to 28 and for the entire 56-d trial. In
contrast, Scollan et al. (2001) suggested that fish oil supplementation had no negative effect on growth performance. Although, Nicholson et al. (1992) reported that fish meal supplementation decreased DMI, it tended to improve feed efficiency by increasing the efficiency of utilization of absorbed nutrients; however, in the current study, fish oil supplementation negatively affected G:F (P < 0.02).
Immune Characteristics No morbidity was observed in either of these studies. Isolated blood lymphocytes (Table 5) from steers fed the corn-based supplement with fish oil had a greater blastogenic response to stimulation with CONA than did lymphocytes from calves fed the corn-based supplement, and there was no effect of fish oil addition to the wheat midd-based supplement (base-supplement × fish oil interaction; P < 0.01). Isolated lymphocytes from steers fed the corn-based supplement had a greater response to stimulation with PHA (P < 0.06) and PWM (P < 0.01) than did lymphocytes from steers fed the wheat midds-based supplements. Fish oil supplementation increased the blastogenic response of lymphocytes to PHA (P < 0.10) and PWM (P < 0.05) over the control steers. In human nutrition, the evolution of immunomodulatory feeds has accelerated during the past 20 yr (Grimble, 2001). The n-3 PUFA are key components of these immunonutrient formulations because of their antiinflammatory actions (Endres et al., 1989; Gerster, 1995; Calder, 1997). This stimulation of the immune system was unexpected because previous studies in humans and rats have shown that fish oil supplementation decreased the activity of the immune system through a decrease in IL-1 and tumor necrosis factor-α production (Hankenson et al., 2000). To our knowledge, this is the first study to evaluate the effects of supplementation of fish oil to ruminant diets on immune characteristics. Fat supplementation in ruminant animals can interact with the absorption and metabolism of other nutrients (Harfoot and Hazlewood, 1997), which suggests that the response observed in the present study might be a result of the effect of fat on the absorption of other nutrients im-
Table 5. Effect of fish oil supplementation on lymphocyte blastogenic response (1,000 × counts/min) Mitogen
Corn
Corn + oil
Wheat midds
Wheat midds + oil
SE
Unstimulateda CONA, 25 µg/mLb PHA, 40 µg/mLc PWM, 15 µg/mLd
2.4z 63z 66 55
3.5yz 88y 79 63
4.7y 80y 60 51
2.4z 76yz 64 53
0.6 4.3 4.6 2.2
Base supplement × fish oil interaction, P < 0.05. Concanavalin A (base-supplement × fish oil interaction, P < 0.01; fish oil supplement effect, P < 0.05). c Phytohaemagglutinin (fish oil supplementation effect, P < 0.10; base supplement effect, P < 0.06). d Pokeweed mitogen (fish oil supplementation effect, P < 0.05; base supplement effect, P < 0.01). y,z Within a row, means that do not have a common superscript letter differ, P < 0.05. a b
Fish oil supplementation to cattle
portant to immune status (Wan et al., 1989) or to a direct effect of n-3 PUFA on the immune system (Calder, 1997).
Implications Results of this study suggest that supplementing fish oil to grazing cattle may boost the proliferative response of lymphocytes and may thereby aid in decreasing morbidity in cattle during the stocker phase of beef production. Nonetheless, the decrease in growth during the grazing and growing phases associated with fish oil supplementation may offset any positive effects of stimulating the immune system. More research may be needed to document the changes in nutrient metabolism caused by fish oil supplementation that might affect immune function.
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