An investigation into the use of infrared thermography (IRT) as a rapid diagnostic tool for foot lesions in dairy cattle

Previous research has suggested that temperature at the coronary band increases in the presence of claw horn lesions in dairy cattle. However the reliability of using infrared thermography (IRT) as a method of distinguishing between lesions has not been investigated. The objective of this study was to examine the potential of IRT as a non-invasive tool for rapidly screening for the presence of digital dermatitis (DD). Eighty-two cows which either had no skin lesions on the hind feet (controls, n=41feet) or a DD lesion on one or both feet were selected during milking. Following selection, each cow was moved into the farm crush where thermal images were taken from the plantar aspect of each foot at the pastern when the foot was dirty, cleaned and raised for visual inspection. Following recording of thermal images each hind foot was trimmed and the presence of any lesion recorded. It was found that the temperature did not differ significantly between feet with DD lesions and other skin or claw horn lesions, regardless of whether the feet were dirty, clean or raised for inspection. As IRT was not sensitive enough for lesion specific detection, the reliability of setting a temperature threshold above which any type of lesion causing lameness could be detected was investigated. The optimal trade off between sensitivity and specificity could be reached without having to either clean or lift the feet. Setting the threshold for disease at 27°C for dirty feet identified 80% of feet with lesions and 73% of feet without lesions correctly. In conclusion, IRT was reliable in detecting elevated temperature associated with foot lesions. Future research investigating the development of lesions may identify a temperature threshold for early treatment intervention. This technique may also be useful to quantify the effectiveness of early treatment by tracking recovery and recurrence of cases.