title: Recombinant bovine somatotropin increases milk yield and calf gain in diverse breeds of beef cattle: associated changes in hormones and indices of metabolism.
abstract: In Exp. 1, Angus (A, n = 30), Charolais (C, n = 37), and Simmental (S, n = 30) multiparous cows received (s.c.) recombinantly derived bovine somatotropin (bST; sometribove, 500 mg) or vehicle (VEH) at 2-wk intervals from 124 to 228 d postpartum (DPP). Calves were weaned at 228 DPP. Bovine somatotropin increased (P < .01) milk yield and percentage of milk fat similarly in A, C, and S cows. Calf weaning weight was greater (P < .05) in cows treated with bST than in those given VEH. Administration of bST decreased deposition of fat and increased concentrations of IGF-I, insulin, glucose, and nonesterified fatty acids. In Exp. 2, we compared effects of bST initiated before or after the breeding season. Charolais (n = 33) and S (n = 40) cows were administered (at 2-wk intervals) VEH or bST beginning at 28 DPP (B-bST) or bST beginning at 105 DPP (A-bST). Calves were weaned at 243 DPP. Administration of bST before or after the breeding season increased milk yield on DPP 136 and 194; however, yields were greater in A-bST than in B-bST cows. Milk yields were similar in all cows at 236 DPP, corresponding to decreased forage availability. Calf body weight was greater (P < .05) in A-bST than VEH; B-bST calves were similar to VEH. Fat depth was greater in VEH than in bST-treated cows in C but not in S cows. Serum IGF-I was greater in A- and B-bST than in VEH cows. Mean days from calving to serum progesterone > 1 ng/mL and pregnancy rates were similar in VEH, A-, and B-bST cows. Administration of bST increased cow milk yield and subsequent calf weaning weight when initiated after 100 d postpartum. As anticipated, bST increased IGF-I, insulin, glucose, and nonesterified fatty acids. Administration of bST before and during the breeding season did not affect reproductive performance.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh 27695-7621, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Armstrong
authors.forename: R W
authors.initials: RW
authors.lastname: Harvey
authors.forename: M A
authors.initials: MA
authors.lastname: Poore
authors.forename: R B
authors.initials: RB
authors.lastname: Simpson
authors.forename: D C
authors.initials: DC
authors.lastname: Miller
authors.forename: G M
authors.initials: GM
authors.lastname: Gregory
authors.forename: G F
authors.initials: GF
authors.lastname: Hartnell
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000502:physiology; D002417:Cattle / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007279:Injections, Subcutaneous / Q000662:veterinary; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008892:Milk / Q000378:metabolism; D014677:Pharmaceutical Vehicles; D011247:Pregnancy; D018873:Pregnancy Rate; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects* / Q000502:physiology
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014677:Pharmaceutical Vehicles; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; C108583:sometribove