1990 Volume 61 Issue 12 Pages 1107-1112
The present experiments were undertaken to investigate the effects of dietary thyroxine (1.2ppm) on the growth, weight of pectoral profundus muscle, rates of muscle protein synthesis and breakdown estimated by Nτ-methylhistidine method and abdominal fat content in the male intact broiler chicken from 15 to 29 days of age in hot(30°C)and moderate (25°C)environments. In the hot environment, dietary thyroxine decreased body weight gain, rate of muscle protein synthesis and abdominal fat content and increased the feed conversion ratio, although pectoral profundus muscle weight and the rate of muscle protein breakdown were not changed. In the moderate environment, dietary thyroxine increased pectoral profundus muscle weight and decreased the feed conversion ratio. However, body weight gain, rates of muscle protein synthesis and breakdown and abdominal fat content did not change significantly. These results indicate that the effects of thyroxine on protein and lipid metabolism in broiler chickens under hot environmental conditions are different from those under moderate environmental conditions.
