The effect of increased air velocity on respirations rate and resting behavior in gestating sows on moderately warm summer days

Heat stress is a challenge for farm animals and animal production, particularly in warmer regions of the world. In pig production, the consequences of heat stress are the adverse effects on animal welfare including behavioral alterations, increased respiration rate, body temperature and mortality and reduced feed intake, milk production and piglet growth rate. The objective of the present study was to investigate the effect of increased air velocity through wall air inlets directed towards the resting area on respiration rate and resting behavior of gestating sows under commercial conditions. The gestating sows were loose housed and chill inlets (including adjustable guiding plates to direct the incoming air in a downward direction) directing air towards the resting area were mounted in one of two resting areas within each pen. The purpose of the latter was to investigate whether the sows preferred to lie in the area with increased air speed. Compared to normal inlets (control) the chill inlets increased the average air velocity from 0.19 to 0.45 m/s (measured 0.4 m above the floor). Respiration rate was recorded and the chill inlets significantly reduced the respiration rate (P < 0.0001). Within the three temperature intervals, 24.4-27.0, 27.1-28.2 and 28.0-32.2 ⁰C, the reduction was 4.2, 6.2 and 7.6 bpm (beats per minute) respectively. There was no difference in percentage of sows resting in the lying areas with activated vs. inactivated inlets.