From hatching to 42 days old, 80 broilers were exposed to varying periods of light (L) and dark (D) within 4-h periods (0.5L to 1.5L and 3.5D to 2.5D). Effects of lighting regimen (LR) and trough position (open (F2) compared with closed (F1)) during D-periods on heat production (H), activity-free (Hacf) and activity-related H (Hac), and respiratory quotient (RQ) were evaluated. At 0.5L and 0.67L, Hac was less than in the longer L-periods. The longer the L-period, the less active broilers were at the end of a L-period. In D-periods with F1, H and Hacf decreased more than with F2, while Hac was similar. After D-periods with F1, H and Hacf increased more than after D-periods with F2. This effect on H was greatest in short L-periods with F1. With 0.5L:3.5D and F1, broilers did not have enough feeding time, because at the end of the L-period afterwards, H and RQ were lower than with the longer L-periods. Thus, broilers will eat feed in the dark and the length of L-period may not be crucial, because in practice, feed will remain available in the dark. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Hourly Changes in Respiratory Quotient and Heat Production after Cessation of Feeding in Cockerels.