Response of laying hens to asymmetrical interrupted lighting regimens: Physiological aspects

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Abstract
1. There were no significant differences in the mean time of oviposition, distribution of ovipositions over the 24 h or proportion of eggs laid in the modal 8 h when conventionally‐lit hens were compared with hens which received interrupted lighting with the same apparent daylength. 2. Intermittently‐lit hens performed 25% less feeding activity than conventionally‐lit hens, but without a significant reduction in mean food intake. There were genetic differences in response of feeding rate to interrupted lighting. 3. Intermittently‐illuminated hens consumed about 20% of their food during the scotoperiods which interrupted the apparent day of a l.5L:0.5D:10(0.5L:0.5D):4L:8D regimen, although there was significant genetic variation from 10 to 22%. None of the genotypes ate during the 8‐h night. 4. Across 4 genotypes neither crop weight nor rate of crop emptying was affected by the lighting treatments, although a heavier mean crop weight under interrupted lighting approached significance in one breed (P<0.10). 5. Interrupted lighting did not cause any ocular disorders.