Andersen, I. L., Ocepek, M., Thingnes, S. L. et al. 2023. Welfare and performance of finishing pigs on commercial farms: Associations with group size, floor space per pig and feed type. Applied Animal Behaviour Science 265, 105979.

Based on data from a field survey of 85 Norwegian farms, we aimed to investigate associations of group size, floor space per pig and type of feed with selected welfare- and performance indicators in finishing pigs. On each farm, we registered the number of pigs per pen, floor space per pig (m2), and the type of feed used (dry feed: n = 42 farms; liquid feed: n = 43 farms), once for every farm between 10:00–12:00 h within the last three weeks before slaughter. Ten pigs per pen from eight pens per farm were randomly chosen for sampling of welfare indicators (bite marks on ears, body and tail, hernia, and movement disorders, and a human approach test). A subsample of 44 farms recorded their production data in the Norwegian Ingris database. These farm level data included daily weight gain, feed conversion ratio, and mean weight of the slaughtered pigs. The pen-level data were analysed using a using a mixed model, with group size and floor space per pig (m2) as fixed effects, type of feed (liquid vs. dry feed) as a categorical variable, and individual “farm” as a random effect. The farm-level data were analysed using a generalized model with Poisson distribution and the same fixed factors. The proportions of pigs with bite marks on ears (P < 0.001) and body (P < 0.001) and daily weight gain (P < 0.001) decreased with increasing group size whereas avoidance of a novel human increased (P < 0.001). The proportion of pigs with bite marks on the body (P = 0.019) decreased with increasing floor space per pig. Providing dry feed ad libitum in vertical feeders resulted in a greater proportion of pigs with bite marks on the ears (P = 0.010) and the body (P = 0.029) than providing liquid feed intermittently in long troughs, but daily weight gain was higher with dry feeding (P < 0.001). Overall, low proportions of pigs had hernias (1.1 ± 0.001%) and movement disorders (1.7 ± 0.2%). In conclusion, our findings indicate that except for an increased avoidance of a novel human in larger groups, the pigs had better welfare in larger groups in terms of lower proportion of bite marks. Finally, more floor space per pig and liquid feed in feed troughs were also associated with a lower proportion of bite marks. As our data were skewed towards smaller group sizes and densities were skewed towards the legislated minimum space allowance per pig, the implications are limited to the range of conditions presented in the study.