May J D, Lott B D
USDA, Agricultural Research Service, South Centrla Poultry Research Laboratory, Mississippi State 39762.
Poult Sci. 1992 Jun;71(6):951-8. doi: 10.3382/ps.0710951.
Broiler chicks obtained from a commercial hatchery were reared on litter in environmental chambers. The rearing temperature was 32 C initially, and reduced 2,8 C/wk until 24 C was reached. Water was available for ad libitum intake. The treatments began at 7 days in Trial 1 and at 8 days in Trial 2, during which feed and water consumption were recorded by computer every 30 min and summarized for 2- and 24-h periods until each trial was completed. In Trial 1, the treatments were: 1) continuous light with feed available 12 h/day; and 2) 12 h light (L):12 h dark (D) with feed available for ad libitum consumption for 1 wk and unavailable thereafter during darkness. In Trial 2, the treatments were 1) 14L:10D; 2) 10L:14D; and 3) continuous light. During the treatments, no feed was provided during darkness and only for 12 h/day during continuous light. At 29 days, feeding and lighting were again continuously provided until the trial ended at 33 days. Broilers were able to anticipate the period of feed unavailability when it coincided with darkness. They were unable to anticipate the period when feed was unavailable if they were in continuous light. Continuously lighted broilers consumed more feed at the onset of the feeding period than did the broilers in light:dark cycles. Periodically lighted broilers consumed more feed at the end than at the onset of the feeding period. Resumption of continuous feeding occurred more quickly for continuously lighted broilers than for those previously on light:dark cycles. The data indicate that the internal clock that permits broilers to anticipate recurring periods of feed unavailability depends on a daily period of darkness.
