Abstract
Four experiments were conducted to investigate the effects of fasting early in life on subsequent performance, mortality and muscle protein metabolism in broiler chicken under high temperature environment. In the first experiment, the effects of 24 hours of fasting at 10 and 20 days of age on performance and mortality were observed in broiler chicken raised under practical conditions in summer. The second and third experiments were conducted to confirm the effect of the fasting on mortality in the same way as the first experiment, while performance was not examined. In the fourth experiment, the effect of 24 hours of fasting at 15 days of age on subsequent 11 days growth and protein metabolism in muscle were clarified using broiler cockerels in hot environment (30°C). In the first experiment, it was indicated. that the 2-day fasts tended to decrease mortality and increase the muscle weight of the birds raised until 59 days of age. In the second and third experiment, mortalities were also lower in the fasted group than the control group, and the difference was statistically significant when the data were subjected to the analysis of variance. The results of the final experiment was consistent with those of the first experiment; both the rates of muscle protein synthesis and breakdown estimated by the Nτ-methylhistidine method were extremely stimulated by the fasting followed by refeeding, but since the rate of synthesis was higher than that of the breakdown, compensatory growth resulted. Thus, the muscle weight of the fasted group was almost the same as that of the control group on the final day of the experiment.
