The adaptation of energy utilization in the laying hen to warm and cool ambient temperatures

Abstract

SUMMARYTwo experiments have been performed to study the acclimatization of laying hens to cool or warm environmental temperature, using the comparative slaughter procedure to measure energy utilization. In the first experiment the energy balances over a 3-week period at either 10 or 35 °C were compared; in the second experiment a comparison was made of the energy balances over six consecutive weekly periods at similar cool and warm temperatures.The first experiment confirmed that production could be maintained (88%) in the warm environment even though food intake was markedly reduced (95 and 63 g/day at 10 and 35 °C respectively). In both environments a loss of body weight indicated, that energy intake was insufficient to meet demands for at least part of the period.During the first week of the second experiment there was a small loss of body weight in the cool environment and food consumption was slightly depressed. The results for energy intake, egg production and heat production suggest that acclimatization was complete after 1 week. In the warm environment egg production fell initially (62%) but returned to a high level (86%) during the second week. However, energy intake, body weight and heat production did not reach steady levels until the fourth week. Comparing the first 3 weeks with the subsequent 3 weeks the daily ME consumption was 137 and 161 kcal/kg¾ and the daily heat production was 126 and 116 kcal/kg¾. Similar, although less marked differences were observed in the cool environment. These results therefore emphasize the need to allow adequate time for acclimatization to the environment in studies of energy metabolism.