The ‘key’ provides a standardised classification for recording skin lesions.
In the course of numerous recent tail biting projects, German investigators developed a common tail and ear lesion scoring key in order to make results more comparable. The key now has a composite nature. Depending on the background of the study, lesions can be scored in different levels of detail which can be combined in order to allow analyses across projects. The provided documents include a summary key, descriptions of scores and exemplary pictures (follow this link for the document in English).
PS German guidelines for the on-farm assessment of farm animal welfare (cattle, pigs and poultry) can be found here (in German).