PSXIV-6 Late-Breaking: Evaluation of the heat tolerance in Girolando cows

Abstract

Abstract The breeds that present better adaptations to the climate of the region where they are raised may present greater productive advantages in relation to those that are less adapted. Considering the tropical regions, it is important to check whether the breeds used have heat tolerance. The aim of this study was to evaluate the heat tolerance of 15 Girolando cows, which was conducted by three evaluations in the months of October, November and December respectively. All evaluations were carried out on sunny days without clouds and little wind. This test consisted of gathering the cows for being compared to each other in a shaded pasture for two hours, from 11 am to 1:00 pm, gauging the physiological parameters at 1:00 pm. Afterwards, the cows were exposed to the open and sunny environment, allowing the total incidence of solar radiation, for one hour (from 1:00 p.m. to 2:00 p.m.), then returning to the shaded corral, being immediately gauging the physiological parameters, and remaining for more one hour, from 2:00 p.m. to 3:00 p.m. assessing again the parameters at 3:00 p.m. The temperature and humidity index found in the evaluations performed at 1:00, 2:00 and 3:00 p.m. hours were 76.6, 77.6 and 78.5, respectively. The mean body surface temperature obtained at 1:00, 2:00 and 3:00 p.m. were 38.16 ° C, 38.90 ° C and 38.22 ° C, respectively. The average values of the sweating rate found were 845.55, 1,088.29 and 955.85 g. m-². h-1 for the measurements performed at 1:00, 2:00 and 3:00 p.m., respectively. The mean values of the rectal temperature obtained at 1:00, 2:00 and 3:00 p.m. were 38.39 ° C, 38.70 ° C and 38.45 ° C, respectively. The evaluated cows showed heat tolerance, suggesting that dairy cattle production systems in the tropics can use Girolando cows.