EFFECTS OF DIFFERENT LIGHTING REGIMES ON DIURNAL FEEDING PATTERNS OF DOMESTIC-FOWL

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. At 10 wk 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. From 15-25 wk 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 photoperiods ate most at the end of the day. When the birds subjected to continuous light were given 1 of the 2 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; those with the dawn and dusk ate more food at the end of the day during most of the 20 day experimental period. The birds apparently preferred to eat most at the end of the day, probably to ensure adequate stores of food in the crop during the night. 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. The difference in growth rate among the 3 treatments may be accounted for by differences in the efficiency of food conversion and food intake.