EVALUATION OF METHODS TO REDUCE FIGHTING AMONG REGROUPED GILTS

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Abstract
The objectives of this study were to evaluate practical methods to reduce fighting among unacquainted pigs after regrouping. One hundred and forty-four gilts of 95–120 kg body weight were assigned to groups of four previously unacquainted gilts and housed in slatted pens of 9.71 m2 floor area for 4 d. At grouping, the animals were assigned to one of the following six treatments: (1) Control. (2) Gilts were washed and Vicks was applied to their nostrils. (3) A boar of 150 kg body weight was housed with the gilts for 2 d after grouping. (4) 2.2 mg kg−1 of Azaperone (Stresnil) was injected intramuscularly 20 min prior to grouping. (5) The pen was equipped with partitions over the feed trough and one partition in the back. (6) Gilts were not fed that morning and were floor fed at grouping. Gilts were weighed and scored for body lesions at the beginning and end of the trial, and were monitored by video recording for 3 d after grouping. The dependent variables were body weights, lesion scores, and time spent standing and walking, resting, or fighting. Weights and variation in weights did not differ between treatments. Partitions in the pen increased lesion scores for front and cheeks of gilts as compared to control gilts. Boar and Azaperone treatments increased time spent standing and walking, Vicks and partitions reduced these activities. Most fighting took place within the first 2 h after grouping. There was no treatment effect on total amount of fighting, but Azaperone changed the temporal pattern of fighting. Since the amount and intensity of fighting were not influenced by treatment, it is concluded that further research efforts should be directed towards the effect that excitement levels at grouping have on fighting and towards devising methods to minimize the damage resulting from fighting. Key words: Swine, behavior, aggression, fighting, mixing