Uses Of Protein Hormones In Animal Production

So many physiological functions are regulated, at least in part, by protein hormones that their potential for use in animal production is enormous. A problem with use of protein hormones is administration. Protein hormones have short half-lives in circulation, less than 20 minutes. Thus, continuous administration of exogenous protein hormones is generally most effective. Injections in aqueous and slow-release depot preparations and osmotic pumps implanted subcutaneously have been efficacious. Transgenic animals have been developed, but technology is not perfected. In 1993, recombinant bovine GH (bST, Posilac®, Monsanto) in a slow release depot preparation was approved for enhancement of milk production in dairy cows in the United States. Use of species-specific recombinant GH has been investigated in beef cattle and swine to improve efficiency and carcass composition. Porcine GH, which is approved in Australia (Reprocin®, Alpharma), improves efficiency of body weight gain 10 to 15% and produces carcasses with more lean and less fat. PMSG has been used to stimulate Graafian follicle growth on the ovary, and either GnRH or hCG are used to induce ovulation in estrous induction and synchronization protocols. There is limited use of FSH in place of PMSG and LH in place of hCG. PG600® (Intervet) is a combination of PMSG and hCG sold in every pig-producing country for induction of estrus in gilts and sows. Immunoneutral-ization of GnRH to reduce boar taint, an androgen in meat from boars that results in an objectionable odor upon cooking, is approved in Australia (Improvac®, CSL Ltd.).

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