Thermoregulatory, behavioral, and productive responses and physical integrity of primiparous and multiparous cows on compost barn in Brazilian tropical conditions.

The compost barn is presented as a system which is capable of providing a suitable environment for dairy cows, but this must be assessed for different climatic regions. Few studies have been carried out evaluating the physics of the thermal environment of this system under tropical conditions. In this study, we evaluated thermoregulatory, behavioral, and productive responses and physical integrity in primiparous and multiparous cows housed in a compost barn system under tropical conditions. From a total of 121 clinically healthy dairy cows aged 3 to 6 years, 30 Girolando cows (7/8) were randomly selected, divided into two groups, according to calving order (primiparous and multiparous), body weight, lactation curve and milk production for the evaluations. Thus, group 1 (primiparous) with an average weight of 524 kg and production of 30 kg was characterized, and group 2 (multiparous) with an average weight and production of 635 kg and 36 kg, respectively. The enthalpy was higher (P < 0.05) in the internal environment of the shed at the three evaluated times (3:30 a.m., 11:30 a.m., and 6:30 p.m.), but the humidity did not vary (P > 0.05) between the internal and external environments at the evaluated times. Respiratory rate was higher (P < 0.0001) in multiparous cows at 11:30 a.m., but was similar at 3:30 a.m. and 6:30 p.m. when compared with primiparous cows. The coat surface temperature was higher (P < 0.001) at 3:30 a.m., but similar at the other two times. For the variables lameness and dirtiness, the vast majority of animals presented scores considered adequate (1 and 2), indicating that it was able to provide an ideal physical environment. Regarding animal behavior, panting (O) and lying idle (OD) were higher (P < 0.05) in multiparous cows. Multiparous cows have higher (P < 0.0001) milk production. Milk production has a negative correlation with enthalpy. The CB system was not able to provide a suitable thermal environment for the animals. Multiparous cows present higher heat stress with change in behavioral responses, especially at midday, but with higher milk production when compared to primiparous cows in compost barn under tropical conditions.