EFFECTS OF THE ADIABATIC EVAPORATIVE COOLING SYSTEM IN FREE-STALL ON PHYSIOLOGICAL RESPONSES IN DAIRY COWS

The purpose of this research was to compare the efficiency of three different schedules using an adiabatic evaporative cooling with misting system (AEC) in a free-stall and its influence on the physiological parameters on lactating cows. A total of 28 Brown Swiss and Holstein multiparous cows were random allocated in four groups. The overall experimental period was of 56 days, starting from January 20th. Treatments were: control group (without AEC); Day (AEC turned on from 7 to 19 h); Night (AEC turned on from 19 to 7 h) and 24 h (AEC turned on during 24h). The dry bulb temperature (DBT), relative humidity (RH) and black globe temperature (BGT) were measuread hourly inside and outside of facilities through a period of 24 hours. The respiratory frequency (RF), rectal temperature (RT) and skin temperature (ST) were registered twice a week at 7, 13 e 21 h. It was observed a positive linear correlation between rectal temperature and ST. The free-stall cooling used in the day group kept the temperature under the thermoneutrality range till 12 h, however from 17 h in the day group the DBT was statistically higher than control and 24 h groups.