LAUSR

Abstract. Animal heat production and transfer data needs updating as genetics evolve, and newer technology provides alternative settings for collecting heat flux measurements. The project objective was to use heat flux sensors to measure the postural (resting, standing) effects on heat flux from finishing pigs, and compare estimated tissue resistance and sensible heat production based on these measurements to literature values. We measured heat flux from 12 individually housed active barrows with average (±SD) weight ranges of 95.6±15.5 kg and 111±13.9 kg, for Trials 1 and 2, respectively. We affixed heat flux sensors to the shaved areas on the right and left sides and rumps of the pigs to collect heat flux measurements every minute over a 6-h period during each trial. An overhead video camera system recorded pig behavior and positioning within each pen throughout the trials. Heat flux measurements showed rapid heat loss between a pig and floor when the pig lies on a cooled surface, but the heat flux starts to decrease almost immediately to steady state levels. When standing, the average heat flux from the rear of the pigs (124±8 W m-2) was greater than the heat flux from the sides of the animal (117±8 W m-2) (p<0.05, n=24). A linear regression model (R2=0.2735, n=24) with an intercept of 143 W m-2, suggests the heat flux decreases 0.25 W m-2 for each 1 kg increase in pig mass. Tissue resistance estimates from these heat flux measurements are approximately 60% of tissue resistance model estimates from the 1990’s. The heat flux data translate to sensible heat production estimates of 1.8 W kg-1, within the range of calorimeter-based estimates from recent literature. Keywords: Heat transfer model, Pigs, Pig housing, Tissue resistance.