Heat stress impact on weight gain in broiler chickens: a meta-analytical study of environmental factor that impact production losses

Abstract

<abstract> <b>Summary</b>: Climatic events can substantially impair the viability of the animals’ production, and the environmental control of broilers facilities improves the production with the reduction in yield losses caused by the heat stress. Our goal was to detect the environmental variables related to the losses of body weight gain (BWG) and the heat stress. This study was based on 52 scientific papers assessed by meta-analysis aiming at heat stress on broilers at 1 to 42 days of age. After meta-analysis examination, data were submitted to data mining techniques in order to obtain decision models for description and quantification of yield losses. The potential reduction of BWG was used as the predictive class. In addition, it was classified as “Appropriate Body Weight Gain” (ABWG, as expected by genetic strain), “Moderate Body Weight Gain” (MBWG, with 16% of reduction on BWG) and “Inappropriate Body Weight Gain” (IBWG, with 36.5% of reduction on BWG). The decision-tree highlighted the mean dry and wet bulb temperatures and the temperature-humidity index (THI) as classifiers with model accuracy of 71.3%. The potential reduction of BWG showed as results 0.82, 0.77 and 0.78 of class precision for “IBWG”, “MBWG” and “ABWG” classifications, respectively. With the meta-analysis, it was possible to evaluate which environmental variables affected the reduction on BWG in consequence of the heat stress. The mean values higher than 32ºC for dry-bulb temperature, 25.5 or 25.7ºC for wet-bulb temperature and 23.3ºC for THI showed to be the threshold triggering within 36.5% in the potential reduction of BWG in broiler production.