EFFECTS OF CHEMICAL INTERVENTION TECHNIQUES ON AGGRESSION AND INJURIES WHEN GROUPING UNFAMILIAR ADULT-PIGS

The effects of a number of 'chemical intervention' techniques and the presence of a boar on the number of aggressive interactions and skin lesions following grouping of four unfamiliar, adult ovariectomized pigs was examined in an experiment involving 24 pigs in five replicates. There were six treatments: two masking odours, a beta-blocker (Suacron), an anti-aggression drug (amperozide), a boar and a control; all treatments were carried out in 1. 8 m X 3.2 m rectangular pens. Aggressive interactions were observed for 90 min immediately following grouping and for 40-min periods around feeding on the day following grouping and 9 days later. Skin lesions were assessed 3 days after grouping. Posture, activity and the spatial use of the pens were also determined during a 60-min period between 14:00 and 16:00 h on the day following grouping and 9 days later. Fewer (P<0.01) aggressive interactions occurred during the period 0-90 min after grouping in the amperozide and boar treatments compared with the other treatments. The amperozide treatment resulted in some vomiting and the boar treatment in mounting activity by the boar, particularly during the first 15 min of grouping (3.75 mounts received per gilt). There were no effects of treatment on aggression around feeding, the number or length of lesions, or the spatial use of the pen during a rest period (P>0.05).