Associations between behavioural indicators of "stress" in weaner pigs and respiratory lesions at slaughter

The aim of the study was to investigate associations on the individual-pig level between eight behavioural indicators of 'stress' (defined in a very general sense), in seven to eight-week old piglets four weeks after weaning and the occurrence of atrophic rhinitis (AR) and chronic pleuritis (CP) at slaughter. The study was designed as a cohort study, including 512 pigs from two commercial farms. With one exception Actinobacillus pleuropneumoniae serotype 2 (App2) infection was not associated with any of the behaviour patterns observed. Using random-effects logistic regression, weak statistical associations, positive as well as negative, were found between the performance of several behaviour patterns and the two pathological lesions. This suggests the existence of biological associations between oral behaviour patterns in young pigs and the health status later in life. However, the results were not consistent between specific oral behaviour patterns or between the two herds indicating that the associations found are either due to chance or reflect the existence of herd-specific confounders. Therefore, results based on studies within only one herd should not be generalized to other herds without care. Behavioural observations on seven- to eight-week-old piglets on the basis of the present investigation cannot be recommended for use as early predictors of AR or CP at slaughter. Further studies are needed in order to elucidate causal relations between behaviour and health.