Investigations on dynamics of social rank of sows during several parities

A total of 939 rank index values from 330 sows were calculated based on the number of wins and defeats during a 48 h mixing period of groups of sows after weaning (8 sows per group) under defined conditions and relations between social rank and parity as well as live weight were analysed. On average the rank index (varying between −1 for subdominant and +1 for dominant sows) rose by 0.12 and the rank position improved by 0.43 from parity to parity. Primiparous sows after weaning of the first litter on average had a rank index of −0.55, a live weight of 184.0 kg and a rank place of 6.4 whereas sows after the 10th parity had a mean rank index of 0.66, an average body weight of 313.6 kg and a mean rank position of 2.1. Sows which had been analysed through 3-4 consecutive parities showed the same tendency. Primiparous sows grouped together with young sows (average parity of the whole group between 1 and 3) had a significantly higher rank index (−0.37, mean rank place 5.7) compared with primiparous sows mixed with older group-mates (parity on average of the group >3) (rank index = −0.71, rank place = 7.0). The rank index of sows after fourth litter was not influenced by the mean parity of the group, but by body weight.