Effect of asymmetrical lighting on the body weight and carcase composition of laying hens and their influence on the efficiency of food utilisation

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Abstract
The body weight, carcase composition and component energy concentrations of laying hens were determined under 17L:7D and 2L:4D:8L:10D lighting regimens. 2. Hens subjected to 2L:4D:8L:10D lighting had lower body weights at end of lay and during most of the laying year, than the 17L:7D control birds. 3. Intermittently illuminated hens had similar absolute water, crude protein and ash contents to, but more water on a proportional basis than, controls. 4. Hens subjected to the 2L:4D:8L:10D lighting regimen had significantly less fat, in both absolute and proportional terms, than the controls. 5. There were no significant differences between the energy concentrations of the fat or fat‐free components of the two lighting groups. 6. There was no significant difference in the regression of fat content on body weight at end of lay for the intermittently and conventionally‐illuminated birds. 7. A prediction of the difference in daily energy requirement, based on egg output, body weight and mean daily body weight gain, very closely matched the actual difference in energy intake. This suggested that the more efficient food utilisation of intermittently‐illuminated hens could be explained by the lower body weight gain of these birds.