Comportamento e variáveis termofisiológicas de bezerros leiteiros mestiços criados em bezerreiro tropical no verão

Abstract

Behavior, thermophysiological variables and the assessment of health scores are important indicators of animal welfare. Thus, the objective of this research was to evaluate the thermophysiological variables, health scores and behavior of crossbred dairy calves raised in a tropical calf, in Triângulo Mineiro, MG, Brazil. This study was carried out in the summer, at the Glória farm, in the city of Uberlândia, Minas Gerais. The average annual temperature varies from 19 °C to 27 °C and its climate is Aw, according to the Köppen classification, with dry, cold winter and low rainfall, while the summer is hot and rainy. Calves' health was assessed by assigning scores (0 to 2), analyzing attitudes, respiratory quality, runny or runny nose, cough, hydration, navel and feces. Respiratory and heart rates and rectal and superficial body temperatures were measured. Air temperature and relative humidity were measured and then the Temperature and Humidity Index (THI) was calculated. Behavioral variables were analyzed with the aid of an ethogram, observing water and food intake, rumination, animals staying in the shade and in the sun, leisure, walking and postures. The differences between the times of the evaluations, for each variable, were evaluated using ANOVA, followed by the Tukey test; and the behavior data by the Friedman test in the IBM SPSS Statistics® version 20 tool (p-value <0.05). Five calves showed changes in the assessment of health scores, with diarrhea and moderate dehydration being the most frequent occurrences. The respiratory rate was lower at 07:00 a.m. in relation to the hours of 11:00 a.m. – 12:00 p.m. and 3:00 p.m. – 4:00 p.m. (45,7; 89,5; 90,4; mov.min-1, respectively), following the increase in air temperature (24.8; 31.3; 32.1 ºC, respectively); however, the rectal temperature remained within the normal limits for the species (38.3; 39.2; 39.5 ºC, respectively. There was no variation in the behaviors observed throughout the day. Despite the increase in air temperature and THI, crossbred dairy calves were able to maintain a constant internal body temperature, and it was possible to observe the maintenance of natural behavior throughout the day. Thus, it is concluded that crossbred calves are indicated for dairy farming in tropical calves in the Triângulo Mineiro, Minas Gerais, Brazil.