Research Note: Validation of a novel scoring system for toe pecking damage in laying hens

Toe pecking is an injurious behavior in commercial laying hens, that can result in pain, tissue damage, loss of toe digits, and mortality. However, little is known about the onset, risk factors and potential interventions for toe pecking behavior. To allow systematic and consistent recording of the prevalence and severity of toe pecking wounds in both research and practice, a validated and easily applicable scoring system would be helpful. Here, a scoring system for toe wounds was developed, ranging from a score of 0 (i.e., normal, greasy, no abnormal scales, no wounds, all nails) to a score of 5 (amputation or severe wound with visible bone or tendons). To validate this scoring system, its associated inter- and intra-rater reliability were determined. A total of 50 severed legs collected from carcasses were scored by five independent raters. Per leg, a score was assigned for the 1) inner toe, 2) middle toe, 3) outer toe, 4) hind toe, 5) topside of the foot, and 6) the lower part of the leg, resulting in a set of six scores per leg (300 scores per rater in total). Moreover, a subset of ten legs was scored twice (independently) to assess repeatability. After exclusion of one rater who appeared to have inadvertently mis-scored left versus right feet, a good inter-rater reliability was observed (intraclass correlation coefficient [ICC] = 0.805, 95%-CI = 0.76-0.84, p < 0.001). Intra-rater reliability of the four raters was good to excellent, with ICC scores ranging from 0.78 to 0.93. Overall, the scoring system for toe wounds developed in this study can help to systematically and consistently record the prevalence and severity of toe pecking wounds in research and practice.