Effects of different degrees of social isolation on the behaviour of weaned piglets kept for experimental purposes

The effect of degree of isolation on the behaviour of weaned piglets was in vestigated using eight replicates of littermates, weaned at 4 weeks and cag ed for 2 weeks in metabolism chambers under varying degrees of isolation: i ) fully isolated without physical contact with littermates; ii) partly isol ated with limited physical contact with littermates; or iii) grouped with t hree littermates. The behaviour of the piglets was video recorded from 0700 h-2230h on days 1, 6 and 13 post-weaning. In addition, a test of behavioura l reactivity towards a novel environment/object was performed on day 8. Irrespective of degree, isolation initially increased the occurrence of beh avioural indicators of stress such as the frequency of pawing and escape at tempts as well as decreasing the frequency of play. In partly isolated pigl ets this initial response was more active than in fully isolated piglets, i ndicating an increased frustration with isolation. Within 2 weeks, however, the stress response in partly isolated piglets had almost completely waned , and they showed only a a decreased frequency of play behaviour, whereas i n fully isolated piglets an increased frequency of pawing as well as a more pronounced reduction of play behaviour were still evident on day 13. Both isolation treatments resulted in markedly lower reactivity in a novel envir onment, seen as fewer squares crossed and fewer vocalizations. It is concluded that social isolation of newly weaned piglets is stressful Although it may increase the initial stress response, provision of social c ontact with littermates, eg through wire mesh, might limit negative long-te rm effects of isolation in experiments where data collection requires indiv idual housing.