Effects of different cooling systems on heat stress and behaviour of dairy cows

This paper shows the results of a research study aimed at investigating the effects of a sprinkler system coupled with forced ventilation on the heat stress and the behaviour of dairy cows reared in a free stall barn without paddock. To this aim, an experiment was carried out inside a free-stall dairy house equipped with two different cooling systems: a fogging system associated with forced ventilation in the resting area and a sprinkler system associated with forced ventilation in the feeding alley. The trial regarded two adjacent pens and the experimental protocol required that the treatment group was housed in one pen where the two cooling systems were always activated following an established timetable, whereas the control group was housed in the adjacent pen, where the sprinkler system associated with forced ventilation was deactivated. Climatic parameters were measured inside each pen of the barn and outside. Then, thermal humidity index (THI) was calculated. Rectal temperature and respiration rate of a sample of dairy cows were monitored each day of the trial. Cow behaviour was monitored by means of a multi-camera video-recording system equipped with 6 cameras in one pen and 4 cameras in the other pen. During the trial, the cows reared in each pen were subjected to mild or moderate heat stress with average daily THI values of about 74. However, during daytime, THI reached values very close to 80, corresponding to a severe heat stress. The physiological parameters values of the treatment group were always significantly lower than the corresponding ones of the control group. Specifically, the sprinkler system especially influenced the respiration rate (56.4 vs 70.1 breaths/min), while it had more limited effects on rectal temperature (38.8 vs 39.4°C). Furthermore, it was observed that the sprinklers influenced the behaviour of the cows. The cows of the treatment group tended to feed more than those of the control one especially when the sprinklers were active. Furthermore, when the sprinkler system was on, cows were encouraged to stand in the feeding alley also without feeding. The results also suggest that the sprinkler system had a positive influence on the behaviour of the cows during night, as the cows of the treatment group tended to lay in cubicles almost for all the nighttime, whereas the control group tended to interrupt the lying activity to go to the rack.