Effects of bovine somatotropin on milk yield and composition, body weight, and condition score of Holstein and Jersey cows.
Forty cows (20 Holstein, 20 Jersey) were administered 0, 5, 10, 15, or 20 mg of recombinantly derived bST daily to determine the effect on milk yield, milk composition, body weight, and body condition score. Administration of bST was from 75 +/- 7 d through 305 d postpartum. A total mixed diet of 45% corn silage and 55% of a concentrate mixture (dry basis) was provided for ad libitum intake. Milk yield of Holstein and Jersey cows administered 20 mg of bST increased 25.3 and 22.8%, respectively, over controls. Fat-corrected milk from Holsteins and Jerseys that were administered 20 mg of somatotropin increased 32.2 and 18.7% over controls, but Jersey response was greatest when 15 mg of bST were administered (27.1% over controls). Dry matter intake of the 20 mg bST group was 13.5% greater than DM intake of controls. Apparent efficiency of production increased linearly with increasing somatotropin. There was no significant change in body weight, but body condition score declined linearly with increasing somatotropin. Most milk composition measures were unaffected by somatotropin. Jersey and Holstein milk yield increased quadratically and linearly, respectively, with somatotropin dose.
West
J W
JW
Department of Animal Science, University of Georgia, Coastal Plain Station, Tifton 31793.
Bondari
K
K
Johnson
J C
JC
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D001947:Breeding; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D007774:Lactation / Q000187:drug effects*; D016018:Least-Squares Analysis; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000032:analysis*; D008894:Milk Proteins / Q000032:analysis; D010298:Parity; D011897:Random Allocation; D011994:Recombinant Proteins / Q000494:pharmacology
D008055:Lipids; D008894:Milk Proteins; D011994:Recombinant Proteins; D013006:Growth Hormone