Impact of feed, light and access to manipulating material on tail biting in pigs with intact tails

Background Tail biting is a welfare issue that also has economic consequences due to infections and illthrift. This study aimed to reduce tail injuries in a high-performing non-tail-docking pig herd with increasing incidences of tail injuries. Results During eleven years preceding the trial, the annual incidence of tail injuries registered at slaughter had increased from 3% to 10%. It was positively correlated to a high weight gain and negatively correlated to day length. The overall incidence of tail injuries during the four years preceding the trial was 9.2% with significant differences between four identical buildings for fatteners (I<II<III<IV). During the adaption period of 6 months and trial period of 12 months, all pigs consumed a feed with increased levels of amino acids, trace elements and fibres, and the four buildings achieved different illumination strategies: I standard fluorescent tubes with an invisible flickering of 30-40% for 14 hours per day; II non-flickering led light for 14 hours per day; III standard fluorescent tubes for 2 hours per day (control); IV similar as III, but with free access to hay silage. During the adaption period, the incidence of tail injuries decreased significantly in all buildings and corresponded to 5.4%. The largest decrease (from 11.4 to 4.3%) was obtained in IV with free access to hay silage. During the trial, the mean incidence of tail injuries decreased to 3.0%. There were no differences in treatment incidences of individual pigs due to tail biting between buildings, but the use of enriched pellets due to anxiety in pens was lowest in II. The incidence of tail injuries in I was significantly higher than in II and III. Conclusions The incidence of tail biting in fast growing non-tail-docked pigs was successfully reduced by supplementing the feed with amino acids, trace elements, vitamins and fibres. Additional manipulative material accelerated that process and non-flickering illumination may have an impact in preventing tail biting. The results obtained argue for the un-necessity of tail-docking pigs, provided that the needs of the pigs in terms of feed ingredients, stocking density and access to manipulative materials are fulfilled.