Investigation into the
causation of belly-nosing in early-weaned piglets
J.M. Gardner, T.M. Widowski,
C.F.M. de Lange and I.J.H. Duncan
University of Guelph,
Guelph Canada
Belly-nosing is a behaviour pattern that characteristically develops in early-weaned piglets. Currently, the factors involved in the causation of belly-nosing are unknown but there is need to understand its motivation and its significance in terms of animal well-being. We conducted two experiments to identify factors that may be responsible for the development of belly-nosing. In the first experiment, we explored the relationships among the establishment of feeding, presence of milk in the diet, diet quality and the development of belly-nosing in piglets weaned at 14-18 days of age. During the first week post-weaning, but not during the subsequent two weeks, piglets offered a poor quality diet ate less (P<0.05) than piglets offered higher quality diets with or without the inclusion of milk products. There were no effects of dietary treatment on belly-nosing (P>0.10). Overall, lower weight-for-age piglets performed more oral-nasal behaviour (nosing/chewing pen-mates, nosing/chewing pen, belly-nosing) than higher weight-for-age piglets (P<0.05). The second experiment explored the relationship between social stress (group composition (mixed litters vs. littermates); density (0.15 m2/pig (HD) vs. 0.4 m2/pig (LD)) and the development of belly-nosing in piglets weaned at 12-14 days of age. Contrary to expectations, aggression was greater for piglets housed at LD than HD (P<0.05). Piglets housed at HD spent more time nosing/chewing a pen-mate than LD piglets (P<0.05). Aggression was correlated with plasma cortisol (r=0.5; P<0.05) and neutrophil:lymphocyte ratio (r=0.35; P<0.05) which suggested a greater stress response in piglets housed at LD. However, there were no differences in belly-nosing for any treatment (P>0.10). In both experiments, belly-nosing developed across all treatments by day 7 post-weaning. The amount of belly-nosing was consistent with that observed in other studies (about 2% of the time) for piglets weaned at 14 days of age. Belly-nosing does not appear to be associated with feed intake, diet quality or diet content of milk products. In addition, belly-nosing appears not to be a general indicator of social stress. Thus far, only weaning age and weight-for-age at weaning appear to be significant factors associated with belly-nosing. Piglets that are less mature physiologically may have a greater need for tactile stimulation obtained through nosing.