Effects of different lighting regimes on diurnal feeding patterns of the domestic fowl

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Abstract
1. Male hybrid chicks were, from hatching, subjected to either a 12‐h photoperiod with uniform light intensity or a 12‐h photoperiod with a simulated “dawn” and “dusk” or to continuous light. 2. At 10 weeks of age the birds exposed to “dawn” and “dusk” were significantly heavier than those exposed to 12 h uniform illumination and these were heavier than those in continuous light. 3. From 15 to 25 weeks of age the birds in continuous light showed a marked diurnal rhythm in food intake, eating most in the period corresponding to normal daytime, while all birds subjected to 12‐h photo‐periods ate most at the end of the day, apparently having learnt to anticipate when their day would end. 4. When the birds subjected to continuous light were given one of the two 12‐h photoperiods, those given 12 h of uniform light intensity started by eating most food in the mornings, but later ate more towards the end of the day, while those with the “dawn” and “dusk”, ate more food at the end of the day during most of the 20‐d experimental period. 5. It is concluded that the birds preferred to eat most at the end of the day, probably to ensure adequate stores of food in the crop during the night. However, it was necessary for them to learn when their day would end, and this they did much sooner with the presence of a “dusk” than without it. 6. It is suggested that the difference in growth rate among the three treatments can be accounted for by differences in the efficiency of food conversion and also by differences in food intake.