Hot chicks, cold feet

Infrared thermography (IRT) is increasingly applied as a noninvasive technique for measuring surface body temperature alterations related to e.g. stress, emotions and leg pathologies in avian species. As a basis for the validation of IRT as a future tool for veterinary diagnostics such as detection and/or prediction of subclinical footpad pathologies in broiler chickens, this study explored effects of manual restraint at two different ages on footpad temperatures. Head region temperatures were applied as additional measures of emotional arousal and stress. The study demonstrated that footpad temperatures dropped during 10min of restraint (p<0.001, -0.45°C 95% CI (-0.49, -0.41) per min), whilst head region temperatures (e.g. nostril, wattle, eye, and average head temperature) rose (p=0.004, 0.76°C 95% CI (0.39, 1.15) per 10min), which is consistent with body temperature alterations during emotional arousal and stress, termed stress-induces hyperthermia. Temperature differed between 30 and 36 d (p<0.001, 1.71°C 95% CI (1.04, 2.38) per week), but it is impossible to draw conclusions whether this effect was caused by age or by conditioning. Furthermore, sequential sampling order affected temperature (p=0.04, 0.13°C 95% CI (0.01, 0.25)). In conclusion, one needs to take into account the duration of handling and restraint during the assessment of footpad temperatures, as well as the chickens age, previous experience and sequential sampling order, when using IRT technology as a future noninvasive tool to study temperature alterations associated with subclinical footpad pathologies in broiler chickens.