Regulation of beef heifer productivity by dietary energy and prepubertal administration of bovine somatotropin
Buskirk, Daniel D.
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https://hdl.handle.net/2142/19509
Description
Title
Regulation of beef heifer productivity by dietary energy and prepubertal administration of bovine somatotropin
Author(s)
Buskirk, Daniel D.
Issue Date
1996
Doctoral Committee Chair(s)
Faulkner, Dan B.
Department of Study
Animal Science
Discipline
Animal Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Agriculture, Animal Culture and Nutrition
Language
eng
Abstract
Weanling heifer calves (n = 452) grazed tall fescue pastures and were fed a high (H) or low (L) amount of corn supplement during a postweaning treatment period of 136 d. Postweaning gain of heifers receiving L and H was.43 and.62 kg/d, respectively. Heifers receiving H were heavier, and had more fat thickness at yearling. More H heifers were pubertal before the breeding season. Mean milk production was greater for H heifers and resulted in heavier calves.
Angus $\times$ Hereford crossbred heifer calves (n = 90) received creep feed for 0, 28, 56, or 84 d before weaning while nursing dams grazing tall fescue pastures. Increasing the length of time receiving creep feed increased rate of gain. The percentage of heifers that were pubertal before the breeding season was linearly increased, and milk production at 52 d postpartum was linearly decreased as time receiving creep feed increased.
Three trials using crossbred heifers (n = 156) were used to determine the effects of dietary energy and bovine somatotropin administration on heifer productivity. In Trial 1, calves were weaned from their dams (n = 28; 113 $\pm$ 13 d of age) and assigned to receive moderate (MDE) or high dietary energy (HDE), and injections of vehicle (VEH) or 250 mg of bovine somatotropin (bST) every 14 d. Heifer calves in Trial 2, (n = 28; 123 $\pm$ 20 d of age) and Trial 3, (n = 100; 134 $\pm$ 22 d of age) nursed their dams while grazing pasture and received no creep feed (MDE) or creep feed (HDE) and received VEH or bST. Treatments were administered for 112 d. There were no dietary x bST treatment interactions. Heifers receiving HDE in Trials 2 and 3 had greater weight and fat thickness by the end of the treatment period. Treatment with bST increased gain in Trials 1 and 2. In Trial 2, HDE decreased milk production, calf weaning weight, and mammary dry fat free tissue and DNA. Treatment with bST in Trial 3, tended to result in increased milk production and calf weaning weights.
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