Respuestas fisiológicas a diferentes ITH en 5 diferentes razas bovinas al norte del Uruguay

The objective of this work was to evaluate the behavior of the Aberdeen Angus, Hereford, Tulianguy, Brangus and Braford breeds against thermal stress. For this, respiratory rate, rectal temperature, body weight, forehead temperature and flank temperature measurements were taken from 1-year-old calves, three days throughout the summer of 2023-2024 in the town of Morató, Paysandú department, a property belonging to the agricultural engineer and farmer Federico García. A comparison of least squares means was made for the variables respiratory rate, rectal temperature, flank temperature and forehead temperature according to breed and THI. Significant differences were observed for all variables as the THI increased, which was expected according to the consulted bibliography. However, significant differences were only observed between the different genotypes at the same THI for the cases of rectal temperature and forehead temperature, with a tendency towards higher temperatures in these areas of the animal being observed for the British Aberdeen Angus and Hereford breeds, indicating that they are more susceptible to heat stress. In the case of respiratory rate and flank temperature, although there was a tendency towards higher values in the British Aberdeen Angus and Hereford breeds, no significant differences were observed between the different genotypes at the same THI. In average daily gain, although there were no significant differences between genotypes, there were significant differences between the different periods evaluated.

A comparison of least squares means was made for the variables respiratory rate, rectal temperature, flank temperature and forehead temperature according to breed and THI. Significant differences were observed for all variables as the THI increased, which was expected according to the consulted bibliography. However, significant differences were only observed between the different genotypes at the same THI for the cases of rectal temperature and forehead temperature, with a tendency towards higher temperatures in these areas of the animal being observed for the British Aberdeen Angus and Hereford breeds, indicating that they are more susceptible to heat stress. In the case of respiratory rate and flank temperature, although there was a tendency towards higher values ​​in the British Aberdeen Angus and Hereford breeds, no significant differences were observed between the different genotypes at the same THI.