Using thermal imaging as a method of investigating thermal thresholds in finishing pigs

Heat production from modern pigs has been determined to be significantly higher than previously reported. This increase in heat production changes the thermal needs of modern growing pigs. A study was designed to evaluate using surface temperatures as a method of determining heat tolerance of growing pigs based on changes in thermal images captured at different temperatures. Thermal images were taken of one hundred sixty group-penned pigs (26.9–62.2 kg) and twenty individual pigs (31.1–57.2 kg) on seven selected days covering a temperature range of 21.3 °C–36.6 °C. The thermal images were analysed to determine either average temperature (individual pigs) or high and low temperatures (group penned pigs). Surface temperatures were significantly affected by ambient temperature and response equations were developed. Breakpoint analysis revealed a threshold, thought to equate to the maximum value of the thermal neutral zone, ranging between 17.4 °C and 23.2 °C. It was concluded that thermal images could be successfully used to evaluate the thermal needs of pigs, and that further experiments need be conducted to validate thresholds as determined by thermal images.

► Thermal images showed changes in skin surface temperatures with changes in ambient conditions.
► Image data were summarised and a breakpoint analysis was used to reveal thresholds.
► This method was proven to be useful in predicting thermal thresholds.
► Images of both groups and individuals resulted in similar thresholds.
► Lower thermal threshold was determined to be between 17.4 and 23.2 °C.