Variáveis fisiológicas e estimativas de trocas de calor em ovinos nativos mantidos em diferentes temperaturas do ar.

Abstract

Sheep, when exposed to high temperatures, as occurs in arid and semi-arid regions, can activate physiological and thermoregulatory mechanisms to increase the dissipation of body heat in latent form, aiming to maintain homeothermia, with heat stress being a significant factor that limits the improvement of sheep in their genetic potential for production and reproduction and, when their ideal temperature is changed, the organism may suffer some type of interference. Therefore, the objective of the research was to quantify the levels of thermal stress, losses of sensible and latent heat in sheep native to the Brazilian semi-arid region, kept in a climatic chamber and subjected to three thermoneutral temperatures (TTN of 20, 24 and 28 °C) and two of thermal stress (TES of 32 and 36 °C). The experimental design used was completely randomized in a factorial scheme, with five temperatures and twenty-four animals. It was observed that with the increase in temperature, the animals significantly (P<0.05) increased rectal and superficial temperatures and respiratory rate. In TTN, sensible heat exchanges corresponded, on average, to 79.64%, while in TES to 20.36%, with latent heat exchanges being 19.73% in TTN and 80.27% in TES. At the highest temperature (36 °C), 95.87% of thermal exchanges were through latent media. Sheep kept in stressful thermal conditions lost the majority of excess metabolic heat by latent means through the skin and respiratory tract.