Gangs of piglets: Welfare and growth of imprinted and guided weaners

Weaning stress accompanied by outburst of aggression is a critical point in pig production as it compromises piglets' welfare and leads to poor growth rate and health problems. Therefore, a weaning methods to smoothen the lactation-weaning transition are of great importance. In the present study a simple practical approach based on the imprinting phenomenon to improve weaned piglets' welfare and growth performance was implemented. From birth, piglets were continually exposed to the simple 2D shapes, either a white circle on a black background (WC) or a black cross on a white background (BC). At weaning, piglets were allotted to weaning groups consisting of one WC and one BC litter, whereby test weaning pens, but not the control pens, were virtually divided using WC and BC signage on respective halves of the pen. The approach was tested in low- and high-density weaning groups, i.e. 10 or 20 individuals per pen (120 animals in total). The results revealed better growth performance of the test group (12-17% higher daily gain). On the whole, the number of post-weaning fights was lower in the test group and the majority of fights (62-75%) occurred among WC and BC. As regards the territoriality, piglets post-weaning tendency to remain in the area marked with a familiar sign was in general significant − i.e. more distinct grouping in the test pens (p < 0.05), comparing to the control pen. It appears that virtual splitting of weaning pens using simple 2D symbols to which pigs were exposed during lactation may decrease weaning aggression, promote distinct grouping and territorial behaviour, and promote growth performance of weaned piglets under farm conditions, especially in groups with lower stock density.