Efeitos do estresse térmico induzido sobre os parâmetros fisiológicos, bioquímicos e hormonais de ovinos nativos de diferentes genótipos em câmara climática

The effect of different temperatures on the physiological, biochemical and hormonal parameters of Soinga, Morada Nova, Santa Inês and SRD sheep was evaluated in a climatic chamber. Twenty-four uncastrated male sheep were used in pens containing 8 animals each (2 from each genetic group), exposed to 3 thermal environments (AT = 28 °C, 32 °C and 36 °C) for a period of 15 days, 10 hours per day. Rectal temperature (RT), respiratory rate (RR) and surface temperature (TS) were measured and hormonal (Cortisol, T3 and T4) and biochemical parameters were evaluated after exposure to each temperature. The thermal environment influenced (p < 0.05) the means of RT, RR and TS. ITGU indicated severe stress from 32 °C (> 84), with a peak elevation at 36 °C (> 88). All genotypes changed physiological parameters as the environment varied, with no difference (P>0.05) between genetic groups. T3 and T4 concentrations were within the reference for the species in all treatments. Cortisol differed (P<0.05) between treatments and genetic groups. There were differences (P<0.05) in mean cholesterol (COL) between treatments and genetic groups and triglycerides (TRI) only between treatment groups with TA=36°C. For glucose (GLI) there were differences (P<0.05) only between treatments. All animals were able to maintain homeothermy even in a heat stress environment, evidencing the adaptive equivalence between Soinga, Morava Nova, Santa Inês and mixed breed (SRD) sheep, due to their high tolerance to heat in extreme environments.