Relationships between individual behavioural traits and post-weaning growth in segregated early-weaned piglets.

Piglets' individual behavioural traits have been studied in the last decade but no report has linked these traits with growth. This experiment was conducted to determine if behavioural traits of segregated early-weaned piglets could be good predictors of their post-weaning growth and, thus, help to predict their adaptation to early weaning. Following segregated early weaning at 17+/-1 days old, 252 piglets were submitted to three tests between 20 and 25 days of age: open-field, reaction to humans and rank order based on competition for a restricted-access feeder. The body weight of each piglet was measured the day before weaning and once a week for the next 4 weeks. A principal component analysis yielded five factors with an Eigenvalue higher than 0.90 that accounted for 81% of the total variation between individuals: reaction to humans (25%), active response to stress (21%), passive response to stress (14%), feeding behaviour (10%) and rank order (9%). Passive reaction to stress was associated with better weight gain during the first week post-weaning (r=0.18; P=0.01), and a positive correlation was found between social status and weight gain during the 4 weeks following weaning (-0.15</=r</=-0.10); P</=0.10). No relation was found between reaction to humans and growth. These results confirm the relationship between rank order and growth in pigs and may suggest that reacting passively to stress could facilitate adaptation to weaning.