Conductive cooling and the metabolism of chicken hens in hot environments

Three studies were conducted to determine the efficacy of water-cooled roosts in the alleviation of heat stress in chicken hens. In the first study, roost preferences and behavioral roosting for thermoregulation purposes were tested. Data on roost use were obtained from time-lapse videotapings. Chicken hens selected square and round-shaped roosts equally (P $\leq$ 0.05). Also 5.0 cm-diameter roost was preferred over smaller-sized roosts ($\leq$0.01). Use of water-cooled roosts increased linearly as the ambient temperature was increased above 25$\sp\circ$C while that of air-equilibrated roosts decreased markedly (P $\leq$ 0.01), indicating that chicken hens used cooled roosts for thermoregulation purposes in hot environments. In the second study, effect of roost temperature on metabolic rate of two strains of chicken hens in hot ambient environments was determined. Indirect open-circuit calorimetry was used to measure the metabolic rates. Water-cooled roosts eliminated the need for deploying energetically expensive thermoregulatory mechanisms for hens in hot environments, lowered the metabolic rates (P $\leq$ 0.01), and reduced mortality. In the third study, effect of roost temperature on productive and reproductive performance of chicken hens in hot environments was determined. Water-cooled roost hens had higher percent hen-day egg production (P $\leq$ 0.05), feed intake (P $\leq$ 0.05), and percent hatchability (P $\leq$ 0.05) than air-equilibrated roost hens indicating that water-cooled roosts improve performance of chicken hens in hot environments.U of I OnlyETDs are only available to UIUC Users without author permissio