(Servi-Tech Laboratories, Dodge City,. KS) for analysis of DM (AOAC Inter- national, 1997; Method 930.15), CP. (AOAC International, 2000; Method. 990.03) ...
The Professional Animal Scientist 31 (2015):30–39; http://dx.doi.org/10.15232/pas.2014-01349 ©2015 American Registry of Professional Animal Scientists
Effects of weaning-period length on growth and health
of preconditioned, spring-born beef calves originating from the Great Plains. II. Early weaning1 E. A. Bailey,*2 J. R. Jaeger,† PAS, T. B. Schmidt,‡ J. W. Waggoner,† PAS, L. A. Pacheco,* D. U. Thomson,§ and K. C. Olson,* PAS *Department of Animal Sciences and Industry, Kansas State University, Manhattan 66502; †Western Kansas Agricultural Research Center, Kansas State University, Hays 67601; ‡Animal Science Department, University of Nebraska–Lincoln 68504; and §Department of Clinical Sciences, Kansas State University, Manhattan 66502
ABSTRACT Angus × Hereford calves (n = 409; initial BW = 163 ± 31 kg) were weaned early (~130 d of age) and assigned randomly to treatments that corresponded to a length of time (d) between separation from their dam and transport to a feedlot: 0 (i.e., nonweaned), 15, 30, 45, or 60 d. Weaning date varied by treatment; transport occurred on a common date and at a common age (160 ± 19 d) for all treatments. Calves were vaccinated against common diseases 14 d before maternal separation and again on the day of maternal separation. Calves were transported 80 d) than are required by industry-sponsored preconditioning programs (≤60 d; Arthington et al., 2005; Rasby, 2007). An evaluation of relatively short (≤60 d) preconditioning programs for early-weaned calves would allow beef producers to compare the risks and rewards associated with a lesser investment of time and capital, relative to long-term preconditioning programs. Therefore, the objective of our experiment was to evaluate the effects of the length of the ranch-of-origin preconditioning period on the health and performance of early-weaned beef calves originating, finished, and slaughtered in the Great Plains.
MATERIALS AND METHODS Experimental Animals All procedures used in this experiment were approved by the Kansas State University Institutional Animal Care and Use Committee. Angus × Hereford calves (n = 409; initial BW = 163 ± 31 kg) from the Kansas State University Commercial CowCalf Unit (CCU; source 1) and the Western Kansas Agricultural Research Center–Hays (WKARC; source 2) were used in this experiment. Calves were spring born (birth date = March 21 ± 20 d) to dams with an average age of 6 ± 2.7 yr. Calves were allowed to nurse dams and to graze native warm-season pastures before weaning. Bull calves were castrated no less than 30 d before the experiment. Calves were vaccinated for clostridial pathogens (Vision 7 with SPUR; Intervet Inc., Millsboro, DE) at approximately 90 d of age.
Treatments Calves were stratified by source, sex, age, and dam age and assigned randomly to treatments that corresponded to a length of time (days) between maternal separation from the dam and shipping: 0 (i.e., nonweaned), 15, 30, 45, or 60 d (n = 81 calves per treatment). The average age of calves at the time of maternal separation was 160, 145, 130, 115, and 100 d for calves weaned 0, 15, 30, 45, and 60 d before shipping, respectively. The experiment was initiated on June 15 (75 d before shipping), and the common shipping date for all treatments was August 24. All treatments had similar average age at shipping (i.e., 160 ± 19 d). All calves received an initial vaccination for infectious bovine rhinotracheitis, bovine viral diarrhea, parainfluenza 3, and bovine respiratory syncytial virus (Bovi-Shield Gold 5, Pfizer Animal Health, Exton, PA) and a vaccination for clostridial pathogens (Vision 7 with SPUR, Intervet Inc.) 14 d before maternal separation. On
the day of maternal separation, calves were immediately transported a short distance (1 and a rectal temperature >40°C were treated with therapeutic antibiotics according to label directions (first incidence = Baytril, Bayer Animal Health, Shawnee Mission, KS; second incidence = Nuflor, Merck Animal Health, Summit, NJ). Treated calves were evaluated 72 h after treatment and re-treated if clinical signs persisted. On the day of shipping, calves from all treatments were weighed individually and shipped approximately 4 h from their respective preconditioning facilities to a single auction market. At the auction market, calves had fence-line contact with other cattle on the premises. Calves were moved through the normal processing and sale facilities to simulate pathogen exposure typically encountered by market-ready calves. Calves were confined to earth-floor pens overnight and offered alfalfa hay ad libitum. At the end of the simulated marketing experience, calves were shipped 1 h to the WKARC feedlot. Upon arrival, calves were stratified by source, weighed, and assigned randomly to a receiving pen by treatment and sex (n = 3 pens per treatment per sex; 13 or 14 calves
per pen). Calves continued to be fed the diet that was introduced during the weaning phase of the experiment for the duration of a 56-d receiving period (Table 1). Health and feeding management during receiving were as described for the weaning phase of the experiment. Diet and ort samples were collected daily from bunks and composited throughout the receiving phase of the experiment. Composited samples were frozen and submitted to a commercial laboratory (Servi-Tech Laboratories) at the conclusion of the experiment. Calf BW were measured on d 25 and 56 following feedlot arrival; DMI and G:F were reported on a pen basis. After the 56-d receiving period, heifers (n = 216) were removed from the experiment and steers (n = 193) were adapted to a finishing diet over a period of 21 d (Table 2). Steers remained in the pens assigned at the time of receiving. Body weights were measured at 60-d intervals during the finishing period and also immediately before slaughter. Subcutaneous fat over the 12th rib was measured via ultrasound (Aloka SSD-500V, 3.5MHz general-purpose transducer array; Aloka Co. Ltd., Wallingford, CT) on d 130 of the finishing phase of the experiment. Using this measurement, steers were assigned to 1 of 3 slaughter dates based on projected time to reach an average carcass endpoint of 12 mm of fat depth over the 12th rib.
Slaughter Once individual slaughter groups reached the targeted carcass endpoint, they were transported to a commercial abattoir. Final BW was measured 24 h before shipment. At the abattoir, lungs were examined for lesions using procedures described by Bryant et al. (1996), and livers were examined for abscesses according to procedures described by Brink et al. (1990). Carcasses were chilled for 48 h and then ribbed and graded. Carcass measurements were collected using digitalimaging software; measurements
Weaning-period length for early-weaned calves
Table 2. Ingredient and nutrient composition of the diet fed to beef calves during finishing Item, % of DM unless otherwise noted Ingredient composition Ground sorghum grain Sorghum silage Soybean meal Limestone Rumensin 801 Ammonium sulfate Salt Tylan 401 Nutrient analysis2 CP Ca P NEm,3 Mcal/kg NEg,3 Mcal/kg
Value 80.9 14.8 3.2 0.5 0.3 0.1 0.1 0.1 13.4 0.32 0.33 1.89 1.25
Elanco (Greenfield, IN). Analyses conducted by Servi-Tech Laboratories (Dodge City, KS). 3 Calculated from nutrient analyses according to NRC (2000). 1 2
included 12th-rib fat thickness, 12thrib LM area, USDA YG, USDA QG, and marbling score (USDA, 1997). Kidney-pelvic-heart fat was measured gravimetrically after dissection.
Cow Management Body condition scores (scale = 1 to 9; 1 = emaciated, 9 = obese; Wagner et al., 1988) were assigned to cows 60 d before and 60 d after the date calves were shipped to the WKARC feedlot. Each cow was viewed and palpated independently by 3 trained evaluators who were blinded to treatment; the average of evaluator scores was recorded. Cows were AI in late June after implementation of a timed-AI synchronization protocol. After timed AI, cows were returned to pastures for 10 d before beginning a 35-d (WKARC) or 50-d (CCU) natural-service breeding season. Delaying natural breeding for 10 d allowed for distinction between AI-bred cows and cows bred
via natural service. Dam pregnancy to timed AI was determined via transrectal ultrasonography (Aloka SSD500V, 7.5-MHz linear reproductive transducer array; Aloka Co. Ltd.) 34 d after insemination. Final pregnancy was determined by rectal palpation approximately 120 d after the end of the breeding season.
Statistical Analyses Growth performance, G:F, and DMI during the weaning, receiving, and finishing phases of the experiment were analyzed as a linear mixed model with one-way treatment structure in a completely randomized design (PROC MIXED; SAS Institute Inc., Cary, NC), with pen serving as the experimental unit. Class factors included treatment, pen, and source (i.e., WKARC or CCU). The model statement included terms for treatment, source, and treatment × source. Carcass characteristics were analyzed as a linear mixed model with one-way treatment structure in a completely randomized design (PROC MIXED; SAS Institute Inc.), with pen as the experimental unit. Incidence of lung lesions and liver abscesses at slaughter were analyzed using PROC GLIMMIX (SAS Institute Inc., Cary, NC), assuming using binary distribution, with pen as the experimental unit. Class factors included treatment and pen. The model statement included only the treatment fixed effect. Cow BCS was analyzed as a linear mixed model with one-way treatment structure in a completely randomized design (PROC MIXED; SAS Institute Inc.). Animal was the experimental unit. Class factors included animal, source, and treatment. The model statement included treatment fixed effect, source fixed effect, and their interaction. Morbidity was analyzed as a generalized linear mixed model with a one-way treatment structure in a completely randomized design (PROC GLIMMIX; SAS Institute Inc.), using binary distribution. Pen was the experimental unit. Class factors included treatment, pen, and source.
33 The model statement included terms for the fixed effects of treatment, source, and treatment × source. The random statement had terms for pen within treatment and source × pen within treatment. The ilink option was used to estimate least squares means and SE of the proportions. Pregnancy data were analyzed as a generalized linear mixed model with a one-way treatment structure in a completely randomized design (PROC GLIMMIX; SAS Institute Inc.), using binary distribution. Pasture was the experimental unit. Class factors included treatment, pasture, and source. The model statement included terms for the fixed effects of treatment, source, and treatment × source. The random statement had terms for pasture within treatment and source × pasture within treatment. The ilink option of SAS was used to estimate least squares means and SE of the proportions. No interactions between treatment and source were detected (P ≥ 0.10) for any analyses; therefore, main effects of treatments were reported. Preplanned contrasts were used to partition treatment sums of squares. Treatment differences were discussed when P ≤ 0.05; tendencies were discussed when P > 0.05 and
