Previous research showed that pigs reared in substrate-impoverished conditions performed a smaller proportion of their total behavioural repertoire in their home pens (showed lower behavioural diversity), than pigs reared in substrate-enriched conditions. This study examined whether these differences were the result of fundamental changes in behavioural organisation. A T-maze task was used to test the hypothesis that substrate-impoverished pigs are prone to develop fixed, unvarying behaviour which may underlie their reduced behavioural diversity. They were predicted to be poorer at reversing previous response patterns in the maze, and less able to alter their behaviour in response to a novel (distracting) stimulus. Female pigs were housed singly for five months in substrate-impoverished pens with bare concrete floors (N = 10) or substrate-enriched pens with straw and other foraging material (N = 10). The pigs were then trained to negotiate a T-maze to reach a food source. There were no differences in responses to a distracting stimulus in the start arm of the maze but, contrary to expectation, substrate-enriched pigs were less able to change their behaviour when the route to food was switched. Thus, the hypothesis was not supported. During training trials, substrate-enriched pigs moved fairly rapidly to the food while substrate-impoverished pigs spent more time investigating the maze; their motivation to 'explore' the maze appeared to override their interest in food. The rapid, food-directed behaviour of the substrate-enriched pigs probably became more fixed and routine-like than the more exploratory behaviour of the substrate-impoverished pigs. The apparent importance of exploration to pigs reared in substrate-impoverished environments suggests that such conditions provide inadequate stimulation.
Mendl, M., Erhard, H. W., Haskell, M., Wemelsfelder, F., & Lawrence, A. B. (1997). Experience in substrate-enriched and substrate-impoverished environments affects behaviour of pigs in a T-maze task. Behaviour, 134(9), 643-659.