title: Injection of synthetic human growth hormone-releasing factors in dairy cows. 1. Effect on feed intake and milk yield and composition.
abstract: Eighteen multiparous Holstein cows in the second half of their lactation were used to determine the effect of human growth hormone-releasing factor (1-44)NH2 and a fragment of growth hormone-releasing factor (1-29)NH2 on lactational performance and feed intake. Saline, the 44-amino acid peptide or the 29-amino acid fragment, at the same dose per injection (.2 nmol.kg-1) was injected intravenously at 4-h intervals for 10 d. Average milk yield, milk composition, feed intake, and feed efficiency were compared for the second half of each 10-d preinjection, injection, and post-injection period. Injections of the 44-amino acid peptide and the 29-amino acid fragment increased milk yield 18.6 and 14.6%, respectively. Feed intake was not changed, but feed efficiency was increased 23.9 and 18.8% over control following 44-amino acid peptide and the 29-amino acid fragment injection, respectively. The lactational response was not different between the two peptides for any of the variables measured. This study demonstrates the feasibility of using a growth hormone-releasing factor fragment as an alternative method of elevating milk yield in cattle via somatotropins.
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004435:Eating / Q000187:drug effects*; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007275:Injections, Intravenous; D007774:Lactation / Q000187:drug effects*; D008892:Milk / Q000032:analysis*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D017337:Sermorelin
chemical_list: D010446:Peptide Fragments; C040786:somatotropin releasing hormone (1-44)amide; D017337:Sermorelin; D013007:Growth Hormone-Releasing Hormone