Hakansson, F., Bolhuis, J. E., 2021. Tail-biting behaviour pre-weaning: Association between other pig-directed and general behaviour in piglets. Applied Animal Behaviour Science 241, 105385.

Tail biting in pigs is a damaging behaviour and remains an economic and welfare problem in modern pig production. Although tail biting has been extensively investigated, little is known about the behaviour in piglets. The aim of this study was to investigate pig-directed and general behaviour and physical characteristics of suckling piglets in regard to tail-biting behaviour. Behavioural data from 284 piglets were collected at a commercial Danish pig unit. Prior to weaning, weight parameters were assessed and the frequency of performed/received pig-directed behaviour (tail biting, tail-in-mouth, tail interest, sow-directed biting, ear biting, other biting, displacement and mounting) and performed general behaviour (play-fight, social contact, suckling, locomotion and resting) was recorded for 60 min/piglet. Piglets were classified after the frequency of performed tail biting into high-biters (HB, ≥3 bites, N = 8), low-biters (LB, 1–2 bites, N = 64) and non-biters (NB, 0 bites, N = 212), and further after their tail damage (TD) into victims (V, TD > 0, N = 134) and non-victims (NV, TD = 0, N = 150). HB were lighter at weaning and had a lower ADG than NB and LB. Both, LB (mean ± s.e.: 0.6 ± 0.2 bouts/h) and HB (0.9 ± 0.3) performed more ear biting than NB (0.2 ± 0.0 bouts/h, P < 0.001), and significant differences between types were found for resting behaviour (percentage of scans ‘resting’: NB: 19.6 ± 1.5, LB: 12.9 ± 1.9, HB: 14.6 ± 4.2, P = 0.001). HB (0.6 ± 0.2) performed more sow-directed tail biting compared to other biter types (0.1 ± 0.0 bouts/h, P < 0.01), performed significantly more ‘other biting’ than NB (HB: 0.5 ± 0.2, NB: 0.1 ± 0.0 bouts/h, P < 0.05), and spent a higher percentage of scans in social contact than NB (HB: 14.7 ± 3.4, NB: 8.1 ± 0.7 bouts/h, P = 0.046). LB engaged more in tail interest (1.7 ± 0.2) compared to other types (0.6 ± 0.2 bouts/h, P < 0.001), displaced other piglets more than NB (LB: 1.1 ± 0.2, NB: 0.6 ± 0.1 bouts/h, P < 0.001) and mounted more than NB (LB: 0.4 ± 0.4, NB: 0.2 ± 0.1 bouts/h, P < 0.001). Moreover, LB (6.6 ± 0.9) spent a higher percentage of scans on play/fight behaviour compared to NB (4.6 ± 0.5, P = 0.042). Both, LB (1.0 ± 0.2) and HB (1.6 ± 0.7) were displaced more often than NB (0.6 ± 0.1 bouts/h, P < 0.001). V mounted more than NV (bouts/h V: 0.4 ± 0.1, NV: 0.2 ± 0.2, P = 0.001), and V received tail interest more frequently than NV (bouts/h V: 1.0 ± 0.1, NV: 0.6 ± 0.1, P = 0.041). This study detected physical and behavioural differences between biter types. The results may suggest that damaging biting behaviours, enhanced activity and social contact are connected. However, no conclusion can be drawn on whether the differences in behaviour are temporal or if they are stable over time. The fact that behavioural differences in regard to tail-biting behaviour were apparent already in piglets may have practical implications for the early prevention and intervention of tail-biting behaviour.