2011 年 48 巻 4 号 p. 229-238
This study was conducted to evaluate the effects of adding methionine (Met) to low-protein diets and subsequent re-feeding on the growth performance, serum lipid profile, body composition and carcass quality in male broiler chicks during 1-42 days of age. During the starter-grower period (1-21 days of age), 800 male broiler chicks (Ross 308) were divided into 5 groups and given the following diets: 1) positive control diet (all nutrients meet the requirements of the strain), 2) negative control diet (low-protein diet in which all amino acids meet the requirements of the strain, except Met), 3) negative control diet supplemented with Met to meet the total sulfur amino acid (TSAA) requirement at 100%, 4) negative control diet supplemented with Met to meet the TSAA requirement at 105%, and 5) negative control diet supplemented with Met to meet the TSAA requirement at 110%. During the finisher period (22-42 days of age), all groups were fed a diet containing the same nutrients and according to the recommendations for the strain. At Day 21, adding Met to the low-protein diet resulted in a similar body weight gain and feed conversion ratio (FCR) to that of the positive control group. Feed intake in the 105% TSAA group significantly increased compared to that in the positive control and negative control groups (P<0.05). Met supplementation in the low-protein diet significantly improved the protein efficiency of chicks (P<0.01), while Met deficiency increased feed cost per body weight gain (P<0.01). Abdominal fat contained in chicks fed the low-protein diet was significantly increased, although Met supplementation slightly decreased the abdominal fat. In the 110% TSAA group, triglyceride in serum was significantly increased (P<0.01), while low density lipoprotein-cholesterol in serum was significantly depressed (P<0.01). After the re-feeding phase (at Day 42 of age), the growth performance of the negative control group was still significantly poorer than that of other groups (P<0.05). Adding Met to the low-protein diet significantly improved the protein efficiency ratio compared to the positive and negative control groups (P<0.05). The body compositions and abdominal fat of broiler chickens did not significantly differ among the treatments (P>0.05). The carcass yield, breast meat and wings of the 110%TSAA group were significantly higher than those of the negative control group (P<0.05). The results indicate that reducing the protein concentration with Met supplementation during 1-21 days of age, then re-feeding with a conventional diet is an appropriated tool for improving overall protein utilization and slightly reduces the production cost.
