Validation of Anatomical Sites for the Measurement of Infrared Body Surface Temperature Variation in Response to Handling and Transport

SIMPLE SUMMARY: The identification of the best anatomical site to ensure the efficient use of infrared thermography to measure body surface temperature variation in response to handling and transport stress may allow easy, non-invasive, real-time and practical animal welfare monitoring under commercial conditions. The objective of this study was to validate the anatomical sites for the measurement of infrared body surface temperature as a tool to monitor the pigs’ response to handling and transport stress. Based on the greatest variation and the closer association with heart rate and salivary cortisol found in this study, the orbital and behind ear regions (in the head) appear to be reliable points for measuring body surface temperature through the technique of thermography in response to handling and transport stress in pigs. However, based on the low to moderate correlations with other physiological indicators, infrared thermography cannot be used as a stand-alone measurement of the physiological condition of pigs in response to stress. Therefore, an appropriate use of infrared technology combined with other physiological stress indicators, e.g., heart rate, blood lactate or salivary cortisol may provide the swine industry with a tool for a real-time evaluation of the physiological condition of pigs during handling and may help to monitor critical areas during the pre-slaughter process improving animal welfare and control meat quality variation. ABSTRACT: This study aimed at validating the anatomical sites for the measurement of infrared (IR) body surface temperature as a tool to monitor the pigs’ response to handling and transport stress. The selected anatomical sites were the neck (infrared neck temperature—IRNT), rump (infrared rump temperature—IRRT), orbital (infrared orbital temperature—IROT) and behind ears (infrared behind ears temperature—IRBET) regions. A total of 120 pigs were handled from the finishing pen to the loading dock through a handling test course. Two handling types (gentle vs. rough) and number of laps (1 vs. 3) were applied according to a 2 × 2 factorial design. After loading, pigs were transported for 40 min and returned to their home pens. Animal behavior, heart rate, rectal temperature and salivary cortisol concentration were measured for validation. Increased IR body temperature, heart rate and salivary cortisol levels were observed in response to rough handling and longer distance walk (P < 0.05 for all). The greatest correlations were found between IROT and IRBET temperatures and salivary cortisol concentration at the end of the handling test (r = 0.49 and r = 0.50, respectively; P < 0.001 for both). Therefore, IR pig’s head surface temperature may be useful for a comprehensive assessment of the physiological response to handling and transport stress.