Individual differences in behaviour, physiology and pathology in breedings gilts housed in groups or stalls

A number of studies in young pigs have demonstrated a relation between a variety of behavioural and physiological features and the degree of resistance displayed early in life in a so-called ''backtest''. The current study aimed at investigating the relation between the backtest response and the development of stereotypies, the circadian rhythm of cortisol, the heart rate response to feeding, and pathological lesions of heart, lungs and stomach of adult breeding gilts.At 10 and 17 days of age, female piglets were subjected to the backtest. In this test, each piglet is restrained on its back for 1min and the number of escape attempts is scored. Pigs classified as high-resisting (HR, n=36) or low-resisting (LR, n=36) were selected and housed in groups of six (3 HR, 3 LR). At 7 months of age, half of the groups were housed in individual stalls.Time spent chain biting by stall-housed gilts during 2h after afternoon feeding was studied at regular intervals for 21 weeks. At 11 months of age, saliva was collected from all animals every hour during 24h for cortisol analysis. At 8 and at 12 months of age, heart rate of all animals was measured around afternoon feeding. Pigs were slaughtered at 14 months of age and heart, lungs and stomach were macroscopically examined.Over time, stall-housed HR gilts tended to show more chain biting, had lower circadian cortisol concentrations and showed a diminished heart rate response to feed delivery compared to LR gilts. In group-housed gilts, the circadian rhythm of cortisol and the heart rate response to feed delivery did not relate to the backtest response. Stall-housed gilts had lower circadian cortisol concentrations than group-housed gilts. The prevalence of pathological lesions was not influenced by backtest type. Stomach wall damage was more severe in stall-housed than in group-housed gilts