Analysis of belly nosing and associated behaviour among pigs weaned at 12-14 days of age

Segregated early weaning is a means of improving disease control and performance in pigs. However, it has been linked to an increased incidence of anomalous behaviours, which raises welfare concerns. A common anomalous behaviour in early-weaned pigs is belly nosing, but the key causal factors of this behaviour are not clear. A study was conducted to examine the incidence of belly nosing and the relationship of belly nosing with other behaviours of early-weaned pigs. Eight pens of 10 pigs, weaned at 12-14 days of age, were videotaped for 24 h on day 7 post-weaning. Behavioural time budgets and partial correlations for each pig were determined by scan sampling at 5 min intervals. Average time spent belly nosing was 2.4% of actual time, with 81% of the pigs belly nosing. Five percent of the pigs spent more than 8% of time belly nosing. Belly nosing was negatively correlated with eating (P < 0.05) and lying (P < 0.05), but positively correlated with standing (P < 0.05), indicating that belly nosing is most common in active piglets. To study the motivation for belly nosing, 25 belly nosing bouts identified by the scan sampling were randomly selected from each of four pens. These bouts were analysed by continuous observation of the nosing pig, beginning 5 min before belly nosing began and concluding 5 min after nosing ended. The average duration of the nosing segment was 538 ± 133.3 (S.D.) s, during which the focal pig spent 65.8% of the time belly nosing with a mean duration of 64 ± 34.7 (S.D.) s per event. For sequential analysis, a χ² analysis was performed for each two-event sequence to determine whether the observed frequencies of any of the sequences deviated from their expected values. The frequencies of social interaction leading to belly nosing (P < 0.01) and belly nosing leading to social interaction (P < 0.05) were higher than their expected values, suggesting that belly nosing and social interaction may share common causal factors. Belly nosing and eating did not occur in sequence frequently, which is indicative that the motivation for belly nosing may be different from eating. Our results suggest belly nosing is more closely associated with social interaction than with eating or drinking.