Beak temperature change in response to acute stress in laying hens measured using infrared thermography

The aim of this study was to investigate beak surface temperature changes to stress induced by fear resulting from tonic immobility using infrared thermography in laying hens. It was also examined whether beak temperatures differed among brown and white lines. The study was based on 89 hens from both lines: 45 White Leghorn birds and 44 Hy-Line brown birds. Beak temperature was measured with infrared thermography immediately before and after tonic immobility testing. The average temperature was obtained from the upper and lower beak area measurements. The beak temperature before tonic immobility had significantly higher temperature than after tonic immobility testing. Birds with shorter tonic immobility had lower temperature of beak than birds with longer tonic immobility. An interaction effect of stimulus (before and after tonic immobility) and tonic immobility time was significant. The upper and lower beak temperatures significantly (P<0.001) decreased in response to tonic immobility test in birds with shorter tonic immobility. Brown hens had higher lower-beak temperature compared to white hens. Based on these results, hens experienced tonic immobility resulting in beak surface temperature changes that were detectable using thermography. Therefore, infrared thermography could be used as a non-invasive technique to assess beak temperature changes in response to stress. Infrared thermography could improve ability to evaluate hens under potentially stressful conditions.