The use of digital infrared thermography and measurement of oxidative stress biomarkers as tools to diagnose foot lesions in sheep

This study reports preliminary data on the use of digital infrared thermography (IRT) and biomarkers of oxidative stress (OS) to diagnose foot lesions in sheep. Interdigital space skin temperatures were obtained from crossbred rams with healthy (n = 9) and with foot lesions (n = 6) with a FLIR T620 series infrared camera. Interdigital space lesions were scored using a five point scoring system (0-4). Blood was sampled from all rams and plasma was analysed for reactive oxygen metabolites (ROMs), biological antioxidant potential (BAP), and advanced oxidation protein products (AOPP). The degree of OS was estimated by the ratio of ROMs/BAP (U Carr/μmol/L) multiplied by 100 to give an OS index (OSI). Footrot scores were used to stratify the rams in two groups: healthy group (HG; n = 9) or foot lesion (FL; n = 6), if the lesions were recorded as absent or present, respectively. Differences in OS biomarkers and IRT temperatures between the two groups were analysed by a linear mixed model. A significant (P < 0.05) increase of IRT temperature was observed in rams with foot lesions compared with healthy rams. Rams that presented foot lesions had significantly higher values of ROMs (P < 0.05) and OSI (P < 0.001) and lower concentration of BAP than healthy rams (P < 0.05). In conclusion, IRT and biomarkers of oxidative stress were able to identify sheep with foot lesions.