Effects of single extensification factors on the occurrence of tail and ear biting, pen fouling and stomach ulcers in finisher pigs raised in conventional indoor husbandry

• Extensification factors affected welfare outcomes differently across indicators • Increased space allowance reduced tail biting, ear biting pen fouling • Lowest stocking density was associated with higher gastric ulcer prevalence • Roughage provision reduced gastric ulcers increased EB and fouling in batch 1 • Enrichment did not prevent tail biting and worsened outbreaks in batch 1 Implementing extensification factors in intensive farming can be a strategy to align with societal needs for better welfare and sustainability, but the effects of individual factors on different aspects of animal welfare remain to be understood. This study investigated the effects of three extensification factors [increased space allowance to 1.4 (S9, n= 108) or 2.1 (S6, n= 72) m2 per pig, provision of various point source enrichments (E, n= 214), daily provision of roughage (R, n= 215)] on the prevalence of tail biting (TB) and ear biting (EB), pen fouling, and stomach ulcers in fattening pigs. Treatments were compared to a control group with 0.7 m2 per pig and no extra enrichment beyond minimum legal requirement nor roughage (C, n= 215). The study was performed over 2 batches, with batch 1 being characterized by an outbreak of TB and fouling in the first 5-6 weeks of study. Overall, the effects of each factor differed according to the welfare indicator observed. S9 and S6 showed benefits in terms of reduction of TB, EB and pen fouling, especially in batch 1, while S6 was associated with a noticeable prevalence of stomach ulceration. In contrast, R led to a clear reduction in stomach ulcers but triggered a significant prevalence of EB and fouling in the first batch. In contrast with expectations, E did not prevent the development of TB and even enhanced the issues during an outbreak of TB in Batch 1. The results show that none of the extensification factors alone improved all aspects of animal welfare, and that some of the factors may result in unexpected negative effects under the given production conditions. This points towards the need for implementing multiple extensification factors in combination to significantly improve animal welfare. Future studies should elucidate how such combination impacts both negative and positive indicators of pig welfare.