Parâmetros fisiológicos e comportamentais vacas 3/4 Holandesas x Zebu no semiárido mineiro

Abstract

The objective of this study was to characterize the condition of thermal comfort as well as physiological and behavioral parameters in 3/4 HolsteinZebu cows, on pasture with offering of natural shade in the Summer and Winter. The experiment was carried out at the Bela Vista farm, family unit, located in the municipality of Verdelândia (MG), 40 km away from Janaúba (MG). We selected 10 3/4 Holstein x Zebu cows, all third calvings, with an average production of 14 kg.dia-1 and an average weight of 570 kg. All animals comprised the middle third of lactation. During the experimental period, measurements of environmental variables daily were made: dry bulb temperature, relative humidity and black globe temperature and subsequently calculated the values of Black Globe Humidity Index (BGHI) and Radiant Heat Load (RHL) for all day. Physiological parameters: rectal temperature, surface skin temperature, respiratory and heart rate were measured after milking morning and evening daily for 15 days. The behavioral parameters were observed during the period when the animals were on the paddock line, following visual and direct observations, with instant registers 12 times a day every 30 minutes, with the aid of an ethogram. The design was completely randomized (CRD) for variables respiratory rate, heart rate, rectal temperature, coat temperature, coat thickness 2x1 (2 times and 1 genetic group). The means were submitted to analysis of variance and F test, at 5% probability. As for climate variables, we used a completely randomized design (CRD) 2x2 (2 times 2 conditions under the sun and under the shade). The data were submitted to analysis of variance and when significant by F test, they were compared by Scott Knott test at 5% probability. Climate variables caused differences in physiological parameters, but they were assimilated by the animal providing welfare. Thus, we conclude that animals are adapted to the climate of semiarid of Minas Gerais region. There were no changes in behavioral activities of crossbred cows in the semiarid of Minas Gerais, possibly due to the adaptation of these animals to the climatic conditions of the region.