The effect of degree of isolation on the behaviour of weaned piglets was investigated using eight replicates of littermates, weaned at 4 weeks and caged for 2 weeks in metabolism chambers under varying degrees of isolation: i) fully isolated without physical contact with littermates; ii) partly isolated with limited physical contact with littermates; or iii) grouped with three littermates. The behaviour of the piglets was video recorded from 0700h-2230h on days 1, 6 and 13 post-weaning. In addition, a test of behavioural reactivity towards a novel environment/object was performed on day 8.

Irrespective of degree, isolation initially increased the occurrence of behavioural indicators of stress such as the frequency of pawing and escape attempts as well as decreasing the frequency of play. In partly isolated piglets this initial response was more active than in fully isolated piglets, indicating 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 decreased frequency of play behaviour, whereas in 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 environment, 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 contact with littermates, eg through wire mesh, might limit negative long-term effects of isolation in experiments where data collection requires individual housing.