Galctopoietic effects of a (1-30)NH2 analog of growth hormone-releasing factor in dairy cows.
Two experiments were conducted to determine the galactopoietic effects of an analog of growth hormone-releasing factor. Specific replacements were made in the AA sequence of growth hormone-releasing factor to produce a growth hormone-releasing factor analog with enhanced stability in vivo. In Experiment 1, 24 Holstein cows were infused i.v. with 0, .33, 1, or 3 mg/d of growth hormone-releasing factor analog for 20 d. Infusion of the analog increased mean serum concentrations of somatotropin, IGF-I, and NEFA. The analog also increased milk yield as much as 44% relative to that of controls. In Experiment 2, 24 Holstein cows were infused i.v. with 0, .11, .33, or 1 mg/d of analog for 60 d. Infusion of analog increased serum concentrations of somatotropin, IGF-I, and NEFA in a dose-dependent manner. At 1 mg/d, the analog increased SCM yield 28% throughout the infusion period relative to the 0 mg/d controls. In summary, a growth hormone-releasing factor analog increased milk yield and serum concentrations of somatotropin and IGF-I. Furthermore, this galactopoietic activity was mediated through the somatotropic axis.
Dahl
G E
GE
Department of Animal Science, Michigan State University, East Lansing 48824.
Chapin
L T
LT
Moseley
W M
WM
Kamdar
M B
MB
Tucker
H A
HA
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000097:blood; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007774:Lactation / Q000187:drug effects*; D008892:Milk / Q000737:chemistry
D005230:Fatty Acids, Nonesterified; C091440:somatotropin-releasing hormone (1-30)amide, Ile(2)-Ser(8)-Ala(15)-Leu(27)-Ser(28)-Hse(30)-; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone