Evaluation of Body Surface Temperature in Broiler Chickens during the Rearing Period Based on Age, Air Temperature and Feather Condition

Abstract

Thermal comfort zone is a crucial importance in broiler chickens to preserve body temperature homeostasis. Since surface temperature contributes to thermal comfort, body surface temperature can be used to evaluate thermal equilibrium in animals. The heat flow at the boundary layer between broilers' bodies and the environment differs between feathered and unfeathered areas. The aim of the present investigation was to adopt linear regression models incorporating environmental temperature and age of birds to predict the surface temperatures of the feathered and unfeathered areas. Temperatures of eight different parts on the body surface were measured using an infrared thermometer during the growth period (1-6 weeks). High correlation between the temperature of feathered regions and air temperature showed that these areas respond faster to changes in the rearing environmental temperature. Six equations were developed for predicting mean surface temperature and also differences between the body surface and air temperature as a function of air temperature, age and feathered or unfeathered body parts. As the air temperature increases, mean surface temperature and difference between body surface values raised and declined, respectively (P<0.05). Similar to the body surface temperature, the effect of age on difference between body surface and air temperature was different for feathered and unfeathered regions. According to the results, it is proposed that the deferent between the feathered and unfeathered areas should be incorporated in the models which used to predict broiler chicken body surface temperature.