Welfare of entire male pigs is improved by socialising piglets and keeping intact groups until slaughter

Abstract

In today's production systems, pigs raised for slaughter are mixed many times, resulting in stress and fighting. The negative consequences of mixing are probably more severe with entire males than with castrates, as they fight more. In this project, we studied a system without castration where entire male pigs met unfamiliar pigs only once. Piglets from two litters were allowed to visit each other from circa 2 weeks of age through an opening between the farrowing pens. Entire males from these litters were kept in intact groups from weaning and onwards, and they were slaughtered pen-wise in 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. In total, 96 entire males from 24 litters were studied. Activity and social interactions of pigs were studied by direct observations on three observation occasions per pen for pigs kept in intact groups and four occasions for control pigs. All pigs were inspected for skin lesions during raising and at slaughter. Results showed that fewer pigs in intact groups were resting (17.1% v. 28.5%; P 5 0.044) and they showed less aggressive behaviour (16.1 v. 27.7 number of interactions per hour; P 5 0.001) than control pigs when moved to the growing-finishing unit. They also got fewer skin lesions compared with control pigs (15 v. 35; P , 0.001). Consequently, control pigs tended to grow slower during the 1st week after mixing; however, growth rate during the whole growing-finishing phase did not differ between treatments (P 5 0.205). Control pigs directed more aggressive behaviour towards non-litter mates than towards litter mates during the whole growing-finishing phase, whereas pigs from the other treatment made no difference between litter mates and other familiar pigs. At 67 kg, there was more sexual behaviour (mounting) among control pigs (7.6 v. 3.4; P 5 0.033), but after slaughter no differences were found in testis weight or boar taint compounds. At slaughter, more entire males that were slaughtered pen-wise and kept in intact groups were without skin lesions compared with the mixed control pigs (74% v. 13%; P , 0.001). This 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.

Influence of social mixing and group size on skin lesions and mounting in organic entire male pigs

“…This is in agreement with Fàbrega et al (2013), who also found more skin lesions in mixed groups compared with stable wean-to-finish groups. In this study, all pigs had been able to socialise with other litters before weaning, which was also the case for the unmixed group in the study by Rydhmer et al (2013).…”

“…As regards mounting behaviour, Rydhmer et al (2013) found more mounting in the intact groups at start and end of the study, whereas Fàbrega et al (2013) found no effect on mounting behaviour in a stable wean-to-finish system compared with mixed groups.…”

“…For entire male pigs, such a procedure could have an even greater impact due to their increased aggression level. Rydhmer et al (2013) found that entire males reared in stable groups showed less aggression and had fewer lesions compared with unfamiliar pigs in mixed groups. This is in agreement with Fàbrega et al (2013), who also found more skin lesions in mixed groups compared with stable wean-to-finish groups.…”

Skatole metabolites in urine as a biological marker of pigs with enhanced hepatic metabolism

“…Animals and sampling A total of 46 entire male pigs of Swedish Yorkshire were recruited from a study on welfare of entire male pigs in relation to socializing piglets, and keeping intact groups until slaughter (Rydhmer et al, 2013). The animals were born and raised at the Swedish Livestock Research Center in Uppsala in accordance with Swedish regulations for use of pigs.…”

“…Animals were, therefore, randomly sampled from the two strata into the subsets used in the present study. Details on management of pigs are documented elsewhere (Rydhmer et al, 2013).…”