Tolerância ao calor de ovelhas rabo largo criadas no Nordeste do Brasil

Abstract

The climatic conditions can affect animal productivity, and it is extremely important to know the conditions that favor adaptation to the heat of native Brazilian breeds. Therefore, the objective of this study was to evaluate theheat tolerance of Rabo Largo sheep raised in a tropical climate, in the Northeast of Brazil. To carry out this work, 5 sheep raised in the Sheep and Goat Sector were used, housed in a collective stall and fed with hay and feed, with access to mineral salt and water. Furthermore, the sheep were exposed to direct solar radiation for 1 hour (12:00 to 13:00h), to evaluate their physiological parameters (respiratory rates-RR and heart rates-HR, rectal temperatures-RT and vaginal temperatures-VT) and surface temperature by infrared thermography. at moments 1) prior to exposure; 2) immediately after exposure, and; 3) after two hours in the shade to assess their thermoregulation. In addition, temperature and relative humidity data were recorded, using a datalogger (AK172) to calculate the temperature and humidity index. The data were submitted to ANOVA at 5% significance. With the increase in thermal discomfort due to direct exposure to solar radiation, given the increase in air temperature which was higher at 1 pm, as well as the THI, it was observed that the sheep's physiological variables increased considerably during sun exposure, in which the RR and HR increased by 109% and 11%, respectively, as well as RT and VT increased by 0.4ºC. However, after placing the sheep in the shade for 2 hours, all physiological parameters returned to normal. Furthermore, the use of thermography helped to identify significant correlations between physiological parameters and surface temperatures at the different moments evaluated. Therefore, it is possible to conclude that Rabo Largo sheep are subject to thermal stress when exposed to direct solar radiation based on the evaluation of their physiological parameters. However, after being placed in the shade, their mechanisms proved to be efficient for physiological normalization.