Coloração do pelame de ovinos mestiços Santa Inês x Dorper submetidos a estresse térmico: respostas fisiológicas e produtivas.

Abstract

The aim of this research was to evaluate the heat tolerance and the yield responses of crossbred sheep Santa Ines with Dorper of white coat and dark under heat stress. The experiment was conducted in September and October of 2012 and was used a completely randomized design. Before and after one hour exposure to solar radiation (14h00 - 15h00), rectal temperature, respiratory rate and the surface temperature of the animals were measured. It were calculated the Index Black Globe Temperature Humidity, the Index of Heat Tolerance and the Coefficient of Heat Tolerance. Measurements of height of the dorsum, rump height, chest width, rump width, thoracic perimeter, thigh perimeter, hind perimeter and scrotal perimeter were made. The animals were slaughtered and were weighed the following components: blood, skin, liver, heart, kidneys, head, legs, lungs, testicles and penis / urethra. The gastrointestinal tract was weighed full and empty. The hot carcass weight (HCW) and cold carcass weight (CCW) and calculated cooling losses (PPR) and hot carcass yield (HCY) and cold (RCF) were evaluated; beyond of the commercial cuts: palette, leg, neck, loin and rib. Finishing and carcass conformation and color assessment (COR), marbling (MARM), texture (TEXT) and subcutaneous fat thickness (SFT) were also evaluated. The values found for the rate of black globe temperature and humidity in the sun and the shade were 89.08 and 82.81 respectively. There was no effect of coloring the hair coat in the rectal temperature of sheep and there was no difference in the rate of heat tolerance. It was verified the effect of the coat colour in the respiratory rate in sheep of dark coat (P < 0.05) and effect of the environment and the color of fur on the surface temperature and on coefficient of heat tolerance in the sun environment. Black sheeps had heavier kidneys than the white sheeps. Testicles, the hot carcass, palette, leg, rib and rump width of black sheeps were lighter towards animals white fur. Sheep with black fur presented lower tolerance to heat. Heat stress can cause disturbances in the metabolism of sheep, affecting their body condition and altering its development.