Índices de conforto térmico para ovinos Santa Inês de diferentes cores de pelame em condições de pastejo

Abstract

The objectives of this work were to determine the best physiological parameter indicator of thermal stress in Santa Inês sheeps, to verify coat color influence on tolerance to heat, to determine the most adequate thermal comfort index for these animals under grazing conditions, and to estimate the critical values of comfort index for short hair Santa Inês breed based on the physiological parameters. The experiment was conducted from January to April in agreste region, of Pernambuco state. The rectal temperature (RT), respiratory frequency (RF), and coat surface temperature (CST) were evaluated three times a week in the morning and in the afternoon. The environment was monitored daily, in a meteorological station installed next to the paddock. The measures for regression and correlation analysis among variables were obtained from 15 Santa Inês sheeps with, five animals for each color: white, chestnut, and black. The obtained results showed that the RF was the best physiological parameter for thermal stress. Thermal comfort index (TCI) and the black globe-humidity index (BGHI) were more accurate than the temperature and humidity index (THI) in the heat stress evaluation on Santa Inês sheep. The correlation and regression results suggested a small superiority of the white animals than the others in the heat tolerance. Basing on the RT, the estimated critical values for white, chestnut, and black sheeps were, respectively, 80.0, 79.5, and 78.9 for THI, 92.8, 91.4, and 90.5 for BGHI, and 46.3, 45.5, and 44.5 for TCI. Basing on the RF, the estimated critical values for white, chestnut and black sheeps were, respectively, 76.3; 75.2 and 75.3 for THI, 86.0, 84.0, and 84.2 for BGHI, and 38.0 for TCI in the animals of the three coat colors.