Drexl, V., Dittrich, I., Haase, A. et al. 2022. Tail posture as an early indicator of tail biting - A comparison of animal and pen level in weaner pigs. Applied Animal Behaviour Science 252, 105654.

The occurrence of tail biting is one of the most important animal welfare problems in pig farming and needs to be recognised early to reduce injuries and suffering. The posture of the tail could be used as an indicator to detect tail biting at an early stage. This study analysed the relationship between tail posture and tail lesions in two different trials within the rearing period of piglets. The aim was to determine whether the tail posture should be recorded at animal or pen level to serve as a reliable early indicator of tail biting. The study used data from 368 (Trial 1) and 480 (Trial 2) pigs that were scored twice a week (11 and 12 scores) within the 40 days of rearing whereby tail posture (lifted or lowered) and tail lesions (lesions or no lesions) were observed. For analysis, a random regression model was used to determine random animal and pen effects on each score for tail posture and tail lesions. Data was analysed using the MIXED procedure of SAS® software. The correlation between tail posture and tail lesions for each score was determined using the random animal and pen effects. Results revealed correlations between tail posture on ScoreX and tail lesions on the successive Score+ 1 (3–4 days between the scores) which showed an increase in Trial 1 from the second to the tenth score at animal (0.32–0.44) and pen level (0.61–0.82). In Trial 2, the correlations ranged from 0.26 to 0.52 at animal and from 0.65 to 0.70 at pen level. The highest correlations (>0.9) were achieved in Trial 2 between scores five and nine. Between tail posture on ScoreX and tail lesions on Score+ 2 (7 days between the scores), the correlations showed a similar development and level as the correlations between ScoreX and Score+ 1. In general, this study identified a relationship between a lowered tail posture and the presence of tail lesions. In addition, this relationship was present a week before the first appearance of tail lesions with stronger correlations at pen than at animal level in both trials. Hence, the farmer should observe the tail posture of animals at pen level during daily inspection in order to intervene early by using appropriate measures against tail biting.