Termotolerância na raça Angus

Abstract

Although meat consumption has decreased in Brazil, exports reached record levels last year. The southeast, central-west, and north states are responsible for the largest volume of production, and the tropical climate limits the use of the Angus breed. The breed could contribute to increasing the sensory qualities of meat. The aim of this study was to evaluate the association of coat color (black or red) and hair coat (classified from 1 to 3, according to the length and thickness of the hair) on the productive and reproductive performance of Angus heifers. The animals were evaluated three times every 45-days, with the third evaluation taking place in January 2022 when the heifers were 18 months old. During all three evaluations, the animals were weighed and classified according to Body Condition Score (BCS) and Reproductive Tract Score (RTS), and in January, in addition to the above, data was collected on internal temperature (IT - intravaginal thermometer), surface temperature (ST - Infrared thermography), sweating rate, and blood samples were collected for serum cortisol evaluation, as well as measurement of the Temperature and Humidity Index (THI) to better understand the results. The results indicated that coat color is related to RTS and IT, with black-coated animals having a higher index of cyclicity, lower IT, and remaining less time in hyperthermia. Hair coat, in turn, was related to weight, BCS, and IT, with animals with thicker coats, particularly coat 3, having lower weight, lower BCS, and spending more time in hyperthermia compared to those with thinner coats. Sweating rate and ST were not different between the different phenotypes. THI data was divided into quartiles to evaluate its influence on animal IT. In general, red and coat 3 animals had higher IT and spent more time in hyperthermia compared to others in all quartiles. Red animals also had higher serum cortisol levels compared to black ones. However, further studies need to be conducted to increase the sample size and accuracy of evaluations, which will serve as a basis for selecting thermotolerant animals.