Effects of feed restriction on heat production, body temperature and respiratory evaporation in the White Leghorn hen on a "tropical" day.

The effects of a shift in the time of feeding on heat production, body temperature and respiratory evaporation in the White Leghorn hen were studied on a "tropical" day. The thermogenic effect of feed at an ambient temperature of 35 degrees C, as compared to 20 degrees C, was delayed for 2 to 3 hours, its magnitude was not as great and the duration was prolonged for 8 to 10 hours. Depriving the chickens of their feed between 0500 to 1200 hours, between 0830 to 1730 hours or for the whole period on a "tropical" day at two different humidity levels did not result in a significant decrease in heat stress during the period with the highest ambient temperature. An ambient temperature range was found in which the body temperature increased while heat production decreased.