Estresse térmico de bovinos leiteiros no sertão central cearense

Abstract

The objective was to evaluate the influence of ambient temperature on the milk production of dairy cows at the Pentecoste experimental farm. Fourteen cows were used, six Brown Swiss and eight Girolando (seven aged 4 to 7 years and seven aged 8 to 11 years), evaluated during both milking sessions (02:00-04:00h and 13:00-15:00h). Environmental variables, including air temperature (AT), relative humidity (RH), and the temperature-humidity index (THI), were measured. Physiological variables included head temperature (HT), ear temperature (ET), nose temperature (NT), dorsal temperature (DT), udder temperature (UT), and respiratory rate (RR). Milk production was measured during both milking sessions. The average temperatures in the milking facility were 25.7ºC in the early morning and 33.9ºC in the afternoon, while relative humidity in the early morning was 75% and in the afternoon was 43%. The temperature-humidity index ranged from 72.1 (early morning) to 83.1 (afternoon). There were no differences between the two age groups for HT, ET, NT, DT, UT, and RR, as well as for RR. However, when evaluating the periods, higher temperatures were observed in the afternoon (P<0.01), with no effect on RR. There was no difference (P>0.01) in milk production between the periods and ages of the animals. The animals may have lower milk production due to the considered moderate stress; therefore, measures should always be taken to mitigate thermal stress, promoting animal well-being and allowing them to reach their maximum production potential.