Effects of pen size, partial stalls and method of feeding on welfare-related behavioural and physiological responses of group-housed pigs

The effects of space allowance (1.97 or 0.98 m2 per pig), partial stalls (presence or absence) and a feeding regimen either within the stalls or on the floor on the welfare of pigs housed in groups of four was examined in an experiment involving 96 pregnant gilts (Large White × Landrace). Welfare was assessed on the basis of skin lesions, changes in social behaviour that may affect welfare (e.g. aggression), the magnitude of any chronic physiological stress response and a measure of cell-mediated immunity. The spatial utilization of the pens by pigs was also observed. The behaviour observations were made when the pigs were initially grouped and over the subsequent 4 weeks. The cortisol concentrations were measured in the fourth and seventh to eighth weeks in treatment; cell-mediated immunity was measured at the end of the experiment In the 90 min following grouping of the (unfamiliar) pigs, the presence of the partial stalls in the pens reduced the number of aggressive interactions (P<0.05−0.01), and there was a trend (P=0.06) for reduced aggression in pens with the smaller space allowance. Feeding in the stalls reduced aggressive interactions around feeding (P<0.01−0.001), and on the day following grouping the presence of stalls per se also reduced the number of aggressive interactions. Both space allowance and design of the pen affected the pigs' spatial utilization of the pen; the effluent channel and stalls were more heavily (P<0.01) utilized in small pens. At the first examination, after 10 days in treatment, there were no effects on the number and length of lesions. Free cortisol concentrations were higher (P<0.001) and cell-mediated immunity was lower (P<0.05) in pens with the smaller space allowance. The treatment of ‘stalls + stall feeding’ resulted in lower free cortisol concentrations (P<0.05), and cell-mediated immunity in this treatment was higher (P<0.05) than in the treatments with no stalls. This experiment has shown there may be welfare advantages, on the basis of reduced aggression immediately after grouping unfamiliar pigs in pens with partial stalls and in the longer term by also feeding in the partial stalls. However, none of the treatments significantly affected the incidence of lesions.