Effects of subclinical footpad dermatitis and emotional arousal on surface foot temperature recorded with infrared thermography in turkey toms (Meleagris gallopavo)

摘要

Footpad dermatitis is a condition that causes lesions on the plantar surface of the footpads in growing turkeys. Potential inflammatory processes and pain associated with increasing severity of footpad dermatitis raise animal welfare concerns. This study investigated whether the temperature of the plantar surface of the foot (the footpads and the entire plantar foot including interdigital membranes) assessed with infrared thermography reflects severity of mild footpad dermatitis as assessed with a Visual Analogue Scale in 80 turkey toms at 10 weeks of age. In order to study effects of a potential emotional arousal due to the testing procedures, effects of sequential testing order and duration of handling of the turkeys was included in the model. Footpad temperatures were significantly lower than foot temperatures (P & 0.001, R-2 = 0.57, -3.36 degrees C +/- 0.28 degrees C), and higher visual analogue scale scores were anti-correlated with footpad (-0.06 degrees C +/- 0.037 degrees C) and foot temperatures (-0.07 degrees C +/- 0.066 degrees C). Furthermore, a negative association between footpad temperature and handling time (-0.02 +/- 0.0227, P = 0.048), and a non-linear association between foot and footpad temperatures and sequential testing order, were found (P&0.001). The results indicate that severity of mild footpad dermatitis as scored visually was associated with the temperatures of the plantar surface of the foot and footpads, and that thermal imaging therefore represents a novel tool for the reliable and non-invasive early detection of subclinical foot pathologies in turkeys. The association was negative, and the findings therefore indicate that potential inflammatory processes in the epidermis at this early stage of footpad dermatitis are negligible, and/or that the hyperkeratosis of the surface keratin shielded heat emission from the footpads. The associations between surface temperatures, handling time, and sequential testing order suggest an emotional arousal in response to the experimental procedures, and these factors need to be considered when applying infrared thermography in future studies of leg health in turkeys.