Assessment of the Level of Heat Stress in Broilers by Measuring Body Temperature and Hyperventilation under Poultry Farm Conditions in Venezuela

Repeated measurements on poultry are difficult to perform in real production conditions because of the difficulty to identify and retrieve the animals. A monitoring technique by which small groups of animals are isolated in wire fence circles within the poultry shed is proposed. This method was used in a production poultry farm in Venezuela to determine variations in body temperature (BT) and the level of hyperventilation (LH), based on the location in the poultry shed and the sex of the animals. Three wire fence circles were set up and divided into two parts, each half-circle containing 20 male or female broilers. From day 29 of age, the ambient temperature (AT) and relative humidity (RH) were continuously registered, and BT (in terminal colon) and LH were recorded every hour from 9:00 to 19:00 every other day for two weeks. The measurements of BT and LH varied during the day, without being completely parallel to the climatic parameters AT and RH. There were significant differences between circles for all parameters measured. The effect of sex was not significant on BT (p = 0.06) but was significant on LH (p = 0.01) and the interaction with the circle location (p < 0.001 for BT and p < 0.01 for LH). Sex had a significant effect on feed consumption (p < 0.01) and weight gain (p = 0.02) but not on the food conversion ratio (p = 0.64). Climatic measurements were also different between circles and between sexes, with in particular a higher RH near males (p < 0.001). Of the overall dataset, BT and LH increased by 0.139°C and 12.1 insp/min, respectively, for each 1°C AT increase. It is concluded that climatic conditions show heterogeneity within the poultry shed, with consequences on the comfort of broilers, and that climatic parameters have to be completed by measurements on animals (BT and LH) in order to characterize the heat stress. The experimental technique proposed here allows observing animals repeatedly in the real conditions of a poultry production farm.