Introduction Since 2008, tail docking is prohibited in EU and in Switzerland but only two of the European countries (Sweden and Finland) have actually implemented it. Tail biting is triggered by lack of enrichment material, bad environmental conditions, unbalanced diet, and disease (Sonoda et al. 2013). The objective of this retrospective study was to assess changes in feeding behaviour of pigs fed a proteins restricted diet before, during and after a tail-biting outbreak. Materials and Methods Seventy-one pigs (117.0 ± 10.7 day old; 47.8 ± 9.7 kg) had restricted (80% of assumed ad libitum intake) access to the grower diet. The diet was formulated to contain 80% dietary crude protein (CP) and essential amino acid (EAA) of the Swiss feeding recommendations. Pigs were housed in a 78 m2 pen with straw in racks and woodchips on the floor. The pen was split into 4 subunits, with 13.39 m2 plain resting area and 6 m2 of slatted floor in each. The pen was equipped with 4 automatic feeders, which allowed measuring the individual feed intake per visit, the number of visits per day and the time spent at each visit. Pigs had ad-libitum access to water through nipple drinkers. Two months after the beginning of the trial, around 75% of the pigs presented tail lesions. The tail-biting outbreak was retrospectively divided into 3 phases (Taylor et al. 2010): the pre-injury phase (A), before tail damage appears, the acute phase (B, once the phenomenon was discovered) and the recovery phase (C, after the tail biting initiator was removed and ad libitum feeding was restored). Each phase lasted 7 days. Total feed intake, average feed intake per visit, maximal consumption per visit, minimum consumption per visit, numbers of visit, and total time spent eating were calculated per pig and per day. The feed efficiency and daily gain were summarized per phase and per pig. For “total feed intake” and “total time spent at the feeder” traits, body weight or total feed intake were respectively included as covariate in the model. Comparisons between phases were performed with R in repeated measures ANOVA (“emmeans and “lme4” packages). Results Except for average feed intake per visit, feeding behavior traits differed (P<0.01) among the phases (Table 1). The total feed intake reported for a standardized bodyweight (48.3 kg) was reduced (P<0.001) in the A and B compared to the C phases, which concurs with the restoration of ad libitum feeding in phase C. In accordance, daily gain was lower (P<0.001) in phases A (0.66 kg/d) and B (0.59 kg/d) compared to C (1.34 kg/d). Total time spent eating adjusted for a defined feed intake (2100 g) was longer in phase A compared to phases B and C, meaning that pigs learn to eat faster and this independently of age. This behavior persisted even when feed was offered ad libitum. Feed efficiency was lower (P<0.05) in phases A and B compared to phase C. One may think this is a consequence of the stress generated by the tail-biting outbreak. Number of visits to the feeder differed (P<0.05) among phases, decreasing from phase A to B and increasing from B to C, and reaching a higher level as in phase A. Table 1 Differences in feeding behaviour traits among the pre-injury (A), the acute (B) and the recovery phases (C) Differences in estimated mean1 P-value Daily feed intake. g/d A-B -6.78 0.961 B-C -656.3 <0.001 A-C -649.2 <0.001 Feed efficiency A-B 0.071 0.338 B-C -0.190 <0.001 A-C -0.119 0.050 Total time spent eating. s A-B 192.2 <0.001 B-C -26.4 0.728 A-C 165.9 <0.001 Number of visits A-B 2.35 <0.001 B-C -0.98 0.006 A-C 1.37 <0.001 1 e.g.: A-B = estimated mean phase A- estimated mean phase B Conclusions Total time spent eating, number of visits and feed efficiency were reduced (P<0.05) before and during the outbreak of tail biting. These finding could be an indicator of a putative increased level of stress. Thus, one can conclude that feeding behaviour traits may be potential forerunner indicators of tail-biting outbreaks. References Sonoda, L. T., M. Fels, M. Oczak, E. Vranken, G. Ismayilova, M. Guarino, S. Viazzi, C. Bahr, D. Berckmans, and J. Hartung. 2013. 'Tail biting in pigs--causes and management intervention strategies to reduce the behavioural disorder. A review', Berl Munch Tierarztl Wochenschr, 126: 104-12. • Taylor, N. R., D. C. Main, M. Mendl, and S. A. Edwards. 2010. 'Tail-biting: a new perspective', Vet J, 186: 137-47.