Effects of dietary lysine and methionine supplementation on Ross 708 male broilers from 21 to 42 d of age (III): serum metabolites, hormones, and their relationship with growth performance

摘要

A previous study has shown that a limited increase of lysine (Lys) and methionine (Met) in broiler diets may improve feed conversion ratio (FCR), BW, carcass yield, and breastmeat yield. This study was conducted to determine the effects of dietary Lys and Met supplementation on various blood serum metabolites and hormones, and their relationship with growth performance and the meat yield of male Ross x Ross 708 broilers. Experimental diets, including 2 Lys levels (100 and 120% of recommended levels) and 4 Met levels (80, 100, 120, and 140% of recommended levels), were fed from 21 to 42 d of age. Blood serum metabolites were not affected by any of the dietary treatments. Uric acid concentration was negatively correlated with absolute weights of the whole body, carcass, pectoralis minor, wing, leg quarter, and front half parts. Cholesterol was negatively correlated with pectoralis major, wing, pectoralis major+minor, and front half. Insulin-like growth factor I (IGF1) and testosterone concentrations were found to be positively related to BW. In addition, positive correlations occurred between concentrations of total protein and high-density lipoprotein cholesterol; uric acid and total cholesterol; and IGF1 and testosterone. In conclusion, dietary amino acid supplementation did not affect the blood serum metabolites investigated, which may be due to the fact that these metabolites are highly regulated in the blood. However, because the expression of genes for these metabolites may be unique to individual birds, growth and the deposition of specific muscles among birds can be quite variable. Even though Lys and Met supplementation improved growth performance, and BW was positively related to circulating IGF1 and testosterone concentrations, these 2 hormones were not affected by dietary Met supplementation. The increase in growth rate caused by dietary Lys or Met supplementation may be due to changes in various integral metabolic pathways as a result of polygenic and pleiotropic relationships, rather than by the isolated effects of individual hormones and metabolites.