Influence of food restriction during rearing on the body composition of layer-strain pullets and hens

The influence of two methods of food restriction during rearing on the body and liver composition of layer-type birds was investigated during and after restriction. In each of two experiments groups of birds were reared on one of three treatments: ad libitum food intake (A), time-limited food restriction (TR) or proportional food restriction (PR). All birds were fed ad libitum during the laying phase. In experiment 1, six birds from each treatment were selected at random for estimation of body and liver composition and killed at 70, 101, 162, 218 and 337 d of age. In experiment 2 four birds were selected from each treatment at 280 and 467 d of age. Body composition was predicted in experiment 2 at various times such as sexual maturity, using equations based on deuterium oxide dilution techniques. Body composition changes caused by food restriction were related to the length of restriction. Towards its end the major changes were: decreased body fat, increased total body water and increased water content of the fat-free mass for TR and PR birds compared to A birds. Some changes were not due to a reduced liveweight. Food restriction during rearing did not change body composition permanently, although predicted body fat at sexual maturity (experiment 2) was lower and protein content higher for TR and PR than for A birds. There was no demonstrable relationship between the body fat content predicted at sexual maturity and subsequent rate of lay (experiment 2).