Correlations among metabolic enzyme activities, their mRNAs and hormone levels in broiler chickens.

Ross 708 broiler chickens were fed one of three levels of crude protein (12, 21 or 30%) from 7 to 28 days of age. Birds were then switched to either higher (12 to 30%, 21 to 30%) or lower levels of crude protein (30-12%, 21-12%). Birds were sampled three days following switches to their respective finisher diets. The purpose of these treatments was to test effects of changes in protein level during the finisher phase (days 28 to 35) of broiler growth and to relate changes to metabolic hormone levels and regulatory enzymes [malic enzyme, ME; aspartate aminotransferase, AAT; isocitrate dehydrogenase (NADP), ICD activities and mRNA]. Glucagon, IGF-I, T4 and Ghrelin were inversely correlated (P<0.01) to ME activities but, positively correlated to both ICD and AAT activities. The data from this experiment also shows that a priority of hormones can be established as far as correlations between circulating value and representative metabolic enzymes and their mRNA's. It is suggested from these data that both IGF-I and T4 are equal in a metabolic priority scheme and are superior to glucagon and Ghrelin which are still significantly related to certain enzymes and their mRNA. It is entirely possible that mRNA levels may not correlate or totally regulate enzyme protein (as evidenced by activities of ME, ICD and AAT activities) although the relationships for ME (R = 0.69; P<0.01) and ICD (R=0.64; P<0.01 were significant. [ABSTRACT FROM AUTHOR]