Thermal comfort evaluation of three genetic lines of nursery pigs using thermal images

Modern swine heat production is 6–41% higher than documented in engineering standards. This higher heat production indicates that the ideal thermal neutral temperature may have changed. Thermal comfort is critical to maximise production and well-being of modern swine. Measurements of posture, skin temperature, and ear temperature profile changes with air temperature were evaluated for three modern pig genetic lines. A total 180 nursery pigs (30 animal per sire – 3 breeds: Duroc, Landrace, and Yorkshire) were acutely exposed to each of seven temperatures (20 °C, 22.5 °C, 25 °C, 27.5 °C, 30 °C, 32.5 °C, 35 °C) over a 13-day period. Time-lapse images were taken every 5-min of 10 pens with 18 pigs each to document posture and floor space. Individual thermal images were captured on 12 pigs/sire-breed – 36 total at each temperature. Thermal images were used to assess trunk and ear surface temperatures. Temperatures along the centerline of the ear were also evaluated for each pig 12 pigs/sire line – 36 total. Changes in the average trunk surface temperature were fit to two separate linear regression equations – above and below the standard temperature of 27.5°C. The two regression lines were solved simultaneously to estimate the thermoneutral temperature. The threshold temperatures were determined to be 26.1°C for Duroc sired pigs, 27.9°C for Yorkshire sired pigs and 28.8°C for Landrace sired pigs. Based on the results of this study the standard set point of 27.5°C is appropriate for nursery pigs.