Estresse térmico em fêmeas bovinas girolando: ¾Holandês ¼GIR vs. ½Holandês ½GIR, criadas em clima semiárido no estado do Ceará

Abstract

The mainly goal of this study was to compare the two most common breed groups of Girolando (½Hol ½Gir vs. ¾Hol ¼Gir) through rectal temperature (RT), respiratory rates (RR), surface temperature (ST), hormonal profiles (T3, T4 and cortisol), milk production, number of inseminations (AI) per pregnancy and pregnancy rates (PR). We used 240 primiparous cows, 120 of each breed group. Physiological data were collected in March, April and May, and in September, October and November. The environmental parameters were: relative humidity (RH), ambient temperature (AT) and the temperature and humidity index (THI). The means of RH, AT and THI were 62.5%, 29.4 °C and 71 in rainy period, and 37.4%, 37 °C and 85 in the dry period, respectively. The RT means and frequencies for ½Hol cows remained within normal ranges in both periods and shifts with differences (p < 0.05) in means inside the rainy period between breed groups. The ¾Hol cows had RT means above of normal ranges in both periods. The RR means and frequencies of ½Hol cows remained within the normal range in both periods and shifts with differences (p < 0.05) between periods. The ¾Hol RR means were above normal ranges during the dry period and differed (p < 0.05) of another group and between periods. In relation to T3, both groups of animals showed higher concentrations in rainy period with differences (p < 0.05) between groups, and there were differences between periods (p < 0.05) in ½Hol group. With the T4 hormone, there were differences (p < 0.05) between the groups in the rainy period and between periods in the group of ¾Hol. In relation to cortisol, there were differences (p < 0.05) in the dry period between the groups of animals and, between periods, for ½Hol animals. In relation to production, there were differences (p < 0.05) in the dry period and, differences between periods, in the other group. At lactation peaks there were differences (p < 0.05) only between periods. In the number of AI there were differences (p < 0.05) between the groups in the dry period and, between periods, in the animals of the group ½Hol. There were differences (p < 0.05) in PR during the dry season between the groups and, between periods, ¾Hol group had a significant decrease in PR in the dry period. The animals best suited to the farm system without cooling are those of the breed group of ½Holstein ½Gir.