Thermoregulatory capacity of Santa Inês hair ewes of different genotypes associated with coat colors raised in a hot environment.

The relationship between hair color characteristics and thermoregulatory responses in ewes raised in hot environment were evaluated. 15 Santa Inês hair ewes of different genotypes associated with coat colors (light brown, dark brown and black) with body weight of 41.2 ± 8.1 kg were evaluated during three consecutive days. Rectal temperature (RT, °C) and coat surface temperature (CST, °C) of seven anatomical points (front, back, croup, loin, side, thigh, and belly) were measured during the morning and afternoon periods. Thermoregulatory responses were recorded along with meteorological variables. Heat tolerance index (HTI) and thermal gradient (TG, °C) were estimated for each genotype. RT and CST were influenced by periods of the day (P < 0.05), being higher in the afternoon, but TG did not differ (P > 0.05) between periods. HTI, CST, and TG were equal (P > 0.05) among the three genotypes. Only RT was higher in animals with dark brown coats compared to light brown, but equal to the black coat. It was observed that animals with black or dark brown hairs have a strong association between the CST under study, and yet these had an inverse behavior with the RT. Animals with a darker coat tend to trigger heat dissipation in various anatomical regions of the body, presenting dynamics in thermoregulatory responses in relation to those with lighter coats. Santa Inês ewes have heat dissipation mechanisms as a function of different genotypes associated with coat colors, but have the same thermoregulatory aspects to maintain homeostasis, demonstrating an excellent adaptive mechanism in a hot environment.