Does weight matter? Exploring links between birth weight, growth and pig-directed manipulative behaviour in growing-finishing pigs

Abstract

Damaging behaviour, especially tail and ear biting, are common problems in modern pig production. It has been suggested that a low birth weight could predispose pigs to become tail biters. Further, previous studies have shown somewhat contradictory links between growth rate and damaging behaviours, as well as resulting lesions. The aim of this study was to investigate, under practical farm conditions, if birth weight and growth of pigs are related to the risk for damaging behaviours and their outcomes, namely tail and ear lesions. A total of 386 pigs were followed from birth until the end of finishing period on four commercial farm pairs (piglet-producing and finishing farms). Based on birth weight, pigs were categorised as Small and Others, and pigs were weighed around weaning and in the growing and finishing units. At the two latter phases, they were scored for lesions and observed for pig- and environment-directed manipulative behaviour (PMB and EMB, respectively). PMB was not more common in Small than in Other pigs. However, PMB in the growing unit was positively associated with growth rate during suckling and growing periods (p = 0.04 and 0.05, respectively) and EMB was reduced in pigs with high growth rate (p = 0.02) in the finishing unit. Additionally, ear lesions in the growing unit were related to high growth rate in both the suckling (p = 0.03) and the growing period (p < 0.01). The current study shows no evidence that low birth weight predisposes to become a performer of damaging behaviours. Instead, a high growth rate in the suckling and growing period increased the risk for a high level of pig-directed manipulation as well as for becoming a victim of damaging behaviour in the growing unit. We suggest that this could be a consequence of increased feeding motivation in fast-growing pigs: they might experience more competition for feed, and consequently a higher level of stress, which predisposes to damaging behaviour.