The use of water-cooled roosts by hens for thermoregulation

Abstract

Experiments were conducted to determine whether hens would use water-cooled roosts for thermoregulation during exposure to high ambient temperatures. In Experiment 1, 8 groups of broiler breeder hens were tested in 25±1 and 35±1°C ambient environments. Each group had access to one water-cooled roost at 20±1°C and two air-equilibrated roosts. In Experiment 2, 6 groups of hens were tested consecutively in 20, 25, 30, 35 and 40δC ambient temperature conditions. Roost temperature was maintained at 20±1°C during the experiment. Two groups were further tested with air-equilibrated instead of water-cooled roosts. Data on roosting behavior were obtained from time-lapse videotapes. In Experiment 1, total roost use was 42.4 and 51.9% in the 25±1 and 35±1°C ambient environments, respectively. Water-cooled and air-equilibrated roosts were randomly used in the thermoneutral (25±1°C) ambient environment. In the 35±1°C ambient environment, the water-cooled roost was used 62.0% of the total roosting time while the two air-equilibrated roosts were used 19.4 and 19.5%, respectively ( P≤0.01). In Experiment 2 roost temperature significantly influenced roost use across the ambient temperature conditions. Use of the water-cooled roost increased linearly ( P<0.01) when the ambient temperature was increased from 25 to 40°C, while that of air-equilibrated roosts decreased. Whereas no panting was observed in hens provided with water-cooled roosts, air-equilibrated roost hen panted vigorously in hot ambient environments. It is concluded from this study that hens sought and used water-cooled roosts for thermoregulatory purposes in hot ambient environments.