Selection for efficiency of food utilisation in laying hens: Causal factors for variation in residual food consumption

Abstract

Abstract 1. Lines selected for high and low values of percentage residual food consumption (PRFC) were compared. 2. Several traits were recorded in order to determine the nature of variation in PRFC: heat production, body temperature, plumage condition, size of comb, wattle and shank, digestibility, abdominal fat content, yolk size and egg quality traits. 3. The difference in adjusted heat production between high and low PRFC groups increased during selection and in the last generation was 120 kj/metabolic body size. Half of the observed difference was attributable to differences in activity. It was found that proportion of yolk, abdominal fat content, total featherless areas and plumage condition made significant but small contributions to the variation in PRFC.