Publications

Personalities in pigs: Individual characteristics and coping with environmental challenges

Bolhuis, J.E.

Summary

There are indications that pigs may have difficulty in adapting to the constraints of intensive housing conditions. Pigs show a wide variation in adaptive responses when exposed to the same stressful situation. Aim of this thesis was to investigate whether the behavioural coping responses of young piglets reflect and predict more general profiles of reactivity to challenges, often referred to as coping styles, under different rearing and housing conditions. For this purpose, pigs were characterized early in life as `high-resisting` (HR) or `low-resisting` (LR) on the basis of their resistance response in a so-called Backtest, in which they were manually restrained in supine position. The major part of the thesis focused on the interaction between these individual coping characteristics of pigs and their housing environment, which was either barren or enriched with straw bedding. The experiments described in this thesis show that HR pigs are more aggressive than LR pigs and less flexible in adapting their behaviour to environmental changes. As the two types of pig differed in response to the dopamine-agonist apomorphine, some initial evidence is provided for a neurochemical background of these behavioural differences. In addition, individual coping or personality characteristics of pigs were reflected in immune reactivity and in their home pen behaviour in barren and enriched environments. HR and LR pigs adapted differently to barren housing conditions. Moreover, individual characteristics modulated the effects of rearing and housing conditions on the behavioural response to novelty, immune reactivity, prevalence of gastric lesions and behavioural development. Remarkably, for almost all of the variables that were affected by housing environment, the impact was much larger for LR than for HR pigs. Thus, individual characteristics of pigs affect their performance in different environments and should be taken into account when studying the impact of housing on their behaviour and welfare. The knowledge of individual coping or personality characteristics could be extended and used for finding the optimal match between pigs and their social and physical environment in pig husbandry.