Effect of human growth hormone-releasing factor (1-29)NH2 on growth hormone release and milk production in dairy cows.
Twelve cows (209 d in lactation, 642 kg BW) were used in an experiment conducted over four 10-d periods (one preinjection, one injection, and two postinjection). Gelatine (n = 6) or 10 mg of growth hormone-releasing factor in gelatine (n = 6) was injected subcutaneously at 1000 h every day on d 11 to 20. Data were averaged for the last 5 d of each period. During the injection period, milk, fat, and protein yields increased by 3 kg.d-1 (14.3%), .14 kg.d-1 (16.7%), and .12 kg.d-1 (15.4%), respectively. Moreover, milk, fat, and protein yields for the treated cows remained higher than for the control cows until the last postinjection period. Growth hormone response was evaluated from blood samples withdrawn from 2 h prior to 8 h postinjection on d 11, 15, and 20 and on d 40. After growth hormone-releasing factor injection, peaks and area under the curve were 24.5, 30.8, and 47.0 ng.ml-1 and 2475, 3979, and 3741 ng.ml-1.min-1 on d 11, 15, and 20, respectively. On d 40, there was no difference in growth hormone concentrations in blood between control and treated cows. These results demonstrate that 10 d of daily injection of a growth hormone-releasing factor increases milk production by 14.3% (3 kg.d-1) and still induces growth hormone release at the end of the injection period without any sign of refractoriness.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007279:Injections, Subcutaneous; D007774:Lactation / Q000187:drug effects*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D017337:Sermorelin
D010446:Peptide Fragments; D017337:Sermorelin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone