Energy repletion and lipid metabolism during compensatory gain in broiler chickens

Ross male broiler chickens were used to determine the effect of dietary energy on metabolism following a 6-day dietary energy restriction. Chickens were fed an amount of food (10 g) from 6 to 12 days of age calculated to only maintain body weight (maintenance energy) and not support appreciable growth. The chickens were then fed 1, 2, or 4x this amount of food for the period from from 13 to 21 days of age. Another group of chickens were also restricted from 6 to 12 days of age, but on an ad libitum basis from days 12 to 21. A control group was fed ad libitum throughout the experiment. All chickens were fed ad libitum from 21 to 54 days of age. Chickens were sacrificed at 12, 15, 17, 19, 22, 28, and 54 days. In vitro lipogenesis (IVL) and enzyme activities (isocitrate dehydrogenase; ICD, malic enzyme; ME, and glutamic oxaloacetic aminotransferase (GOT) were determined during the 12 to 28-day period and at 54 days. All restriction groups were lighter (P < 0.05) than controls at 28 days. Only chickens given 1x and 2x maintenance energy from 12 to 21 days were lighter (P < 0.05) than controls at 54 days. The 6-day energy restriction decreased (P < 0.05) IVL and ME and refeeding 2x and 4x maintenance restored IVL as did refeeding ad libitum. The greatest response was noted between 2 and 4 days following refeeding, surpassing controls at both periods. The significance of the present study lies in the findings that lipogenesis can be dosed against the energy intake following restriction and that changes in lipogenesis are very rapid, reaching steady state within 2 to 3 days. Furthermore, the growth data suggest that restriction regimens shift normal growth curves and compensatory growth may be an artifact of expressing data because smaller, younger birds have less fat than older birds.