Influência do resfriamento no curral de espera sobre o microclima, a fisiologia e a produtividade de vacas leiteiras

Abstract

Animal cooling technologies have improved the environment in production systems worldwide, providing animal well-being by meeting thermal comfort requirements in high external temperatures, as has been observed in recent years due to constant changes in climate conditions. This study aimed to evaluate the effect of a cooling system using sprinklers and fans in the holding pen for lactating cows by evaluating thermophysiological and behavioral variables, milk production, and thermal environment. Twelve lactating Girolando cows, primiparous, with a lactation interval of 120 to 180 days, were evaluated. They were subjected to two treatments (without and with spraying and ventilation) for six days each. Respiratory rate (RR), forehead temperature (FT), udder temperature (UT), rumination or watering behavior, and daily milk production were measured. The collected data were evaluated using the Student's t-test, except for some variables such as forehead temperature, rumination frequency, drinker frequency, and morning relative humidity. The nonparametric Wilcoxon test was used for these variables. However, in both tests, a significance level of 5% was used, with p < 0.05. Morning cooling provided a reduction of 1.15°C in the maximum temperature and 1.34°C in the minimum temperature of the holding pen, resulting in a Temperature and Humidity Index (THI) and Equivalent Temperature Index (ITE) of 68.32 and 25.94°C, respectively. In the afternoon, the system also reduced the maximum temperature by 2.96°C and the minimum temperature by 3.11°C, resulting in a THI and ITE of 77.06 and 30.75°C, respectively. In the physiological responses of the cows, it was possible to observe in the morning, a reduction in respiratory rate (53.44 r.p.m.), forehead temperature (29.39°C) and udder temperature (32.76°C) in relation to without cooling, which presented results such as: FR (74.36 r.p.m.), TF (30.08°C) and TU (34.27°C). In the afternoon, with cooling, these variables also presented lower values of: FR (59.06 r.p.m.), TF (31.54°C) and TU (34.24°C) in relation to without cooling, with values of: FR (91.97 r.p.m.), TF (34.06°C) and TU (36.64°C). Milk production did not differ between treatments with and without cooling. Regarding behavior, there was a higher frequency of rumination and lower frequency of use of the waterer with the cooling system. Therefore, the sprinkler and ventilation system was effective in providing thermal comfort to the animals in the morning and afternoon. However, it requires adjustments to increase its effectiveness in the afternoon regarding microclimate.