Happier Together: Socialising piglets improves welfare of entire male pigs
The animal Article of the Month for September is entitled ‘ Welfare of entire male pigs is improved by socialising piglets and keeping intact groups until slaughter’
Surgical castration is painful and should be avoided to improve pig welfare. Entire males do, however, perform much more sexual behaviour than castrates and repeated mountings can decrease the welfare of pen mates. Entire males also show more aggressive behaviour towards unknown pigs than castrates do. Pigs raised for slaughter are often mixed with unknown pigs many times and each mixing results in stress and fights, and sometimes injuries. The negative consequences of mixing are more severe with entire males than with castrates, since entire males fight more. There is one occasion in a pig’s life when mixing is ‘natural’ and not associated with fighting. That is at two weeks of age, when the sow leaves the isolated farrowing nest and brings her piglets to the group. We studied a system without castration where entire males met unfamiliar pigs only once, and at an early age. Our aim was to improve welfare by creating groups of familiar entire males with a group size appropriate for conventional growing-finishing units.
Piglets from two litters were allowed to visit each other from two weeks of age through an opening between the farrowing pens. Entire males from these litters, called ‘friends’ were kept in intact groups from weaning and onwards, and they were slaughtered pen-wise in these intact groups. Control pigs were raised and weaned in their litters and mixed with unknown pigs when moved to the growing-finishing unit. They were slaughtered by split marketing based on individual weight. We recorded activity and social interactions of the pigs by direct observations. All pigs were also inspected for skin lesions during raising and at slaughter.
‘Friends’ showed less aggressive behaviour than control pigs when moved to the growing-finishing unit. They also got fewer skin lesions compared to control pigs. Consequently, control pigs tended to grow slower during the first week after mixing. Growth rate during the whole growing-finishing phase did, however, not differ between control pigs and ‘friends’. Control pigs directed more aggressive behaviour towards non-litter mates than towards litter mates during the whole growing-finishing phase, whereas ‘friends’ made no difference between their litter mates and the other pigs in the group. At 67 kg, ‘friends’ performed less sexual behaviour than control pigs, but after slaughter there were no differences in testis weight or boar taint compounds. At slaughter, less ‘friends’ (slaughtered pen-wise and kept in intact groups) had skin lesions compared with the mixed control pigs.
Our study shows that the welfare of entire male pigs can be improved by socialising piglets and by keeping them in intact groups during raising and at slaughter. However, this management routine does neither improve growth rate, nor decrease boar taint.
Authors: L. Rydhmer, M. Hansson, K. Lundström, C. Brunius and K. Andersson
The animal Article of the Month is selected by the Editor-in-Chief and is freely available for one month.