Effects of regrouping on the individual behavioural characteristics of pigs

Abstract

The behaviour of an animal is a combination of that which is inherited and that which is influenced by the environment. This study was conducted to determine a means for assessing and distinguishing individuals based on behavioural characteristics and to better understand the environmental impact on behavioural trait changes in pigs. Eighty-nine pigs (nine litters) were followed from birth until the end of the grow–finish period. All litters remained intact until four were mixed when they entered the grow–finish phase. Data on general activity, social behaviour, average daily gain and injury scores were collected throughout the entire experimental period. When the pigs were still with the sow, we also collected data on teat order consistency, suckling and suckling bouts. The pigs were subjected to a series of behavioural tests when in the nursery and grow–finish phases. The data were subjected to a factor analysis to determine individual behavioural traits. The effect of regrouping was determined by using an analysis of variance, comparing scoring coefficients of pigs that either remained intact or were regrouped. Three primary factors were identified and interpreted as indicating levels of approachability, exploration, and aggression. Regrouped and intact treatments only differed in level of approachability. The intact litters followed a typical habituation response to repeated exposures of a novel arena test. However, the pigs in the regrouped litters consistently took longer to approach a human and novel object. This suggests that the trauma caused by regrouping resulted in a generalisation of fear associated with an environmental change.