Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 1998
Publication Date: N/A
Technical Abstract:
Despite well documented anabolic effects of GH in mammals, a clear demonstation of such a response in domestic poultry is lacking. Comprehensive dose-response studies of GH action in the chicken have been conducted using recombinant chicken GH by means of i.v. infusion at 8 weeks of age. GH reduced feed intake body weight gain in a dose dependent manner. .Somatic changes were not secondary to GH-induced anorexia, as birds pair fed to the level of voluntary intake of GH-infused birds did not differ from controls. The reduction in feed intake may involve centrally-mediated mechanisms as hypothalamic neuropeptide Y protein and mRNA were reduce. Growth of breast muscle was also reduced in a dose-dependent manner, however, muscle 3-methyl-histidine content was not changed, suggesting that a depression in protein synthesis rather than increased degradation occured Breat muscle IGF-I was not enhanced by GH, despite evidence that early events in the GH signaling pathway were intact. A GH dose-dependent increase in circulating triiodothyronine concentrations paralleled decreases in hepatic monodeiodinase activity. This confirms that a marked hyperthyroid response to GH occures in late posthatch chickens, resulting from a decrease in the degradative pathway of T3 metabolism. This secondary hyperthyroidism would account for the decreased skeletal muscle mass and lack of enhanced tissue IGF-I in FH treated birds. Based upon these studies, it is now evident that GH does in fact have significant, important effects in poultry, but that secondary metabolic responses confound the anabolic potential of the hormone
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