Modification of the Purdue Hog Cooling Pad Control Scheme Design for Heat Stress in Gilts

Abstract

<b><sc>Abstract.</sc></b> The Purdue hog cooling pad was recently retrofitted with an electronic control system that allowed for intermittent flushing of the cooling water. Intermittent flow control schemes based on temporal or temperature threshold triggers were previously evaluated using lactating sows for the overall heat transfer rate from animals and the quantity of heat removed per liter of cooling water. Studies were planned to evaluate the ability of the cooling pad to mitigate heat stress in boars. Mitigation of heat stress in boars is beneficial to commercial hog operations by preventing decreases in semen quality and quantity due to overheating. Before a statistical study could be undertaken, a preliminary scoping study of the range of control scheme parameters for the boar experimentation was needed. As the high value of boars and their long recovery time from periods of heat stress precluded conducting large numbers of trials on boars, gilts were evaluated as a substitute, due to their similar level of heat production. Temporal flow control schemes with four min and eight min OFF times, followed by a 30 s flush were examined, as well as temperature threshold control schemes with trigger temperatures of 28.0°C and 29.5°C. The respiration rate and rectal temperature of each animal were measured and used as indicators of heat stress in the gilts. The range of appropriate heat removal rates was identified, and a hybrid control scheme that utilized both temporal and temperature threshold control was determined to be the best control scheme for future studies on mitigating the effects of heat stress in boars.