Conforto térmico de instalações para bovinos em feira agropecuária no Nordeste

Abstract

Ceará is a state where agribusiness is quite significant. Due to its predominantly semi-arid climate, animals at agricultural fairs may experience thermal discomfort, limiting their ability to maintain homeothermy, especially for less adapted breeds. Therefore, the aim was to characterize the facilities and thermal exchanges of cattle and their environment during an agricultural exhibition in Ceará. A total of 35 animals were used, grouped by breed and physiological state, including lactating cows from the Jersey (5), Pardo Suíço (5), and Girolando (5) breeds; dry Gir cows (5); pregnant Guzerá cows (5); Sindi heifers (5); and Nelore bulls (5). The animals were housed in north-south oriented sheds, with open sides, a sand bedding, and a fiber-cement roof, arranged in a tie-stall system under semi-humid tropical climate conditions. The animals had free access to the feeder and were led to the water trough three times a day. Data was collected at 7 AM, 12 PM, and 6 PM. Environmental variables as air temperature, relative humidity, and the temperature-humidity index (THI) to assess environmental discomfort. The surface temperature of the animals was measured as the average of the temperatures of the forehead, thorax, and rump regions using an infrared thermographic camera. Thermographic images of the sand bedding and fiber-cement roof were also taken, as well as an evaluation of the heat exchange between the animals and the facility. Data were analyzed using ANOVA at a 5% significance level. The highest air temperature was recorded at 12 PM (33.0 ºC; p<0.05), along with the lowest relative humidity (52.9%; p<0.05) and the highest THI (82.6; p<0.05). Thermography indicated variations in the animals' surface temperatures throughout the day, with higher values at 12 PM. The floor and roof also showed elevated temperatures at noon (34.9; 49.0; p<0.05). The temperature gradients between the animal's surface, the sand bedding, and the environment were smaller at 12 PM for all groups. Thus, it can be concluded from the environmental parameters that at 12 PM, the animals experienced greater thermal stress, classified as moderate, and during this period, heat exchange by conduction was less effective due to the lower temperature gradient between the animals and the facility.