Relationship between starvation heat production and body size in the domestic fowl

The relationship between starvation heat production (SHP) in kJ/d and body weight (W) in kg for the domestic fowl was examined by compiling calorimetric data on 78 immature and 222 mature fowls. Linear regression analyses were performed after transformation of the data to a logarithmic scale (base = 10). The derived relationship (re-transformed) for mature birds was found to be: SHP = 406 W0.602 The weight exponent (b) was significantly (P less than 0.01) different to the value of 0.75 normally used for mature birds.

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).

The effect of food restriction during rearing on fasting heat production of layer strain pullets and hens

Fasting heat production was measured in darkened respiration chambers at three chronological and three physiological ages during rearing and laying in a layer strain to determine the effects of food restriction during rearing. There were three rearing treatments (42 to 162 days of age) in which birds were allowed ad libitum food intake (F) or were restricted by time (TR), in which birds were allowed continuous ad libitum food intake for about 24 hr in every 72 hr, or by proportion (PR), in which birds were offered each day 60 to 70% of the quantity consumed by F birds the previous day. Liveweight at 163 days of age was reduced by 19 and 15% for TR and PR birds, respectively, compared to F birds. Ad libitum food consumption was allowed during the laying period. Chronological age measurements were carried out at 140 days of age (prelay), 332 days of age, and 370 days of age. Physiological age measurements were carried out at sexual maturity (first egg), peak production (28 days after first egg) and postpeak production (98 days after first egg). Fasting heat production, measured under conditions that minimized physical activity, was not altered after correction for liveweight changes by the food restriction treatments. Based on this and other published studies, it was postulated that physical activity may play an important role in determining the effects of food restriction in poultry.