Temperatura corporal e comportamento de vacas leiteiras em pastejo

Abstract

Brazil is a country with a tropical climate and one of the main problems faced by dairy farmers is that of heat-stress, which as well as causing physiological and behavioral changes, reduces milk production. The objective of this study was to monitor the body temperature of dairy cows when grazing and the patterns of behavior presented by them as a result of the environmental conditions to which they were subjected and to understand the factors involved. The experiment was conducted on the Glória Experimental Farm, of the Universidade Federal de Uberlândia, in Uberlândia-MG. Forty three (43) crossbreed cows were used, of which 16 were multiparous and 27 primiparous. Milk control was accomplished and parameters such as respiratory rate, body temperature and behavior were monitored, as well as environment temperature and humidity. Body temperature presented a positive correlation with milk production (r=0,02) and with the humidity and temperature index (r=0,40). The respiratory rate presented a positive correlation with temperature humidity index (r = 0,68) and body temperature (r = 0,61). Animals with body temperature below 39,1ºC presented an increase of 66% in the probability of being grazing, when compared with animals with body temperature above this value. Animals submitted to conditions of a high humidity temperature index (>68) have an 85% greater chance of not being grazing than those animals in conditions of low humidity temperature index(<68). It is important to know the relationship of the animal with the environment in which it is inserted, since it exerts great influence on the physiology and productive performance of the animals.