Fattening pigs display weak behavioural changes due to gastric ulcerations

Summary

Gastric ulcers and erosions in the stomach are a common health problem in fattening pigs. However, such changes can only be assessed after slaughtering. Potential behavioural indicators that allow for an early detection would be favourable. In a study with 147 male (entire and castrated) fattening pigs kept in groups of three, we conducted behavioural observations for 2 days shortly before slaughtering with an average live weight of 102 kg. We recorded body positions, feeding, drinking and social interactions. After slaughtering, stomachs were inspected for signs of erosions or ulcers. First, behavioural outcomes were modelled using linear mixed effect models with random, but without fixed effects. The residuals obtained were then analysed with linear discriminant analysis (LDA). In a second step, the prevalence of gastric ulceration was analysed using a generalised linear mixed effect model with behavioural variables as fixed effects. From 96 focal pigs, 16 (16.7%) were found to have erosions or ulcers. The LDA did not reveal satisfactory levels of correct classification. While it was possible with this approach to classify healthy pigs as healthy (93.7%), pigs with erosions or ulcers were classified only partially as sick (6.2%). By modelling the gastric ulceration score with behavioural variables, we found that affected pigs tended to lie more in contact with other pigs, to show more manipulations of pen mates and to significantly lie longer in total and feed longer on concentrate.
These results indicate that there are small differences in behaviour between healthy and affected pigs. Automated behavioural observations with a higher resolution could provide more insights into how pigs show pain or discomfort due to gastric ulcerations.