Bulens, A., Van Beirendonck, S., Van Thielen, J. et al. 2018. Rearing finishing pigs with intact tails: Do they benefit from an enriched environment? Journal of Veterinary Behavior 24, 1-8.

In an attempt to prevent tail biting in pigs, tail docking is often done. This management procedure is painful for the pigs, so the question arises whether pigs can be raised with intact tails and whether these pigs would benefit from an enriched environment. The aim of this study was to investigate the behavior and performance of fattening pigs with intact tails in an enriched environment and fattening pigs in a more barren environment. A total of 94 pigs with different genetic backgrounds (type C pigs: predisposed to better carcass traits vs. type G: predisposed to better growth) were followed up during the fattening period (30-110 kg). Half of these pigs (n = 48) were housed in 4 barren control pens (a hanging toy as enrichment). The other half of the pigs (n = 46) were housed in 4 enriched pens (a hanging toy, straw blocks in a dispenser, and a hiding wall). Type C and type G pigs were equally spread over these treatments, but were housed separately (n = 2 pens/type/treatment). Behavioral observations were carried out once a week, and the presence of skin lesions was recorded every 14 days. Pigs were weighed individually on 4 occasions (start of the study, 6 and 12 weeks later and at slaughter), and simultaneously, tail lengths were also measured. The results revealed a general higher frequency of ear biting compared to tail biting in both barren and enriched pens. However, a higher frequency of tail biting was observed in enriched pens in the period between weight 3 and slaughter (90-110 kg) compared to barren pens. The restriction of movements around the pen and restricted access to the straw dispensers caused by the hiding wall, in combination with decreased space allowance due to weight gain, might have resulted in increased tail biting. When looking at the entire fattening period, this higher frequency of tail biting in enriched pens was mainly observed in type G pigs, while no difference between barren and enriched pens was found for type C pigs. Pigs in enriched pens had a higher average daily weight gain over the entire fattening period. Pigs predisposed to better growth (type G) had a higher average individual weight and longer tails than pigs predisposed to better carcass traits at the start of the fattening stage, yet daily weight gain and daily growth of the tail over the entire fattening stage did not differ between pig types. In conclusion, the presence of both straw dispensers and a hiding wall did not contribute to a lower frequency of biting behavior and aggressive behavior. Tail biting increased in enriched pens during the last period of the fattening stage. The results suggest that genetic background should be considered when investigating the cause of tail-biting outbreaks and when evaluating the effect of enrichment on tail biting.