Individual behavioural differences in pigs: Intra-and inter-test consistency

Individual differences in behavioural responses are of increasing interest in the behavioural sciences. There could be enormous benefits for animal husbandry if a test could be developed that would identify categories or types of individuals unlikely to cope with subsequent challenges. The present study compared the behavioural responses of two series of 16 groups (n - 6 or 7 gilts) under four different circumstances: Situation 1, an open field with a novel stimulus (bucket or human); Situation 2, individual access to food for 15 min after a 20-h period of food deprivation; Situation 3, competition for food after food deprivation; Situation 4, general activity and feeding behaviour in a group over a 24-h period. Situations 1 and 2 were assessed four and three times over a 2- and 1-week period, respectively. Both showed high levels of consistency in the behavioural responses of the gilts. Principal component analyses were used to reduce the number of variables per test situation and facilitate measurement of consistency across test situations. The amount of variation explained by the first component was generally more than twice that explained by any subsequent components. The only significant correlation between factor scores calculated from the first components was found between Situations 1 and 2 in the first series. None of the calculated factor scores showed bi- or multimodal distributions. We conclude that, whilst over a short period of time gilts respond consistently to a specific challenge, they do not display the same consistency when challenged in a different context. This lack of inter-situation correlations, plus the absence of multimodal distributions, fails to support the view that behavioural 'types' of gilts exist.