Abstract
Objective: To examine the effect of group housing sows on their behavior and fertility.
Materials and methods: In Experiment One, at 65 to 70 days of gestation, 96 sows were assigned by parity to individual or group housing and observed for aggressive encounters during three 1.5-hour time blocks immediately after relocation and 1 day later. On the third day, feeding-time aggression was observed during two 30-minute feeding periods, starting when feed was dropped. Saliva samples obtained from unrestrained sows 1 day before and after relocation were assayed for cortisol concentrations. In Experiment Two, 937 mixed-parity sows in 10 weekly breeding groups were either housed in groups of approximately 50 (n = 462) or individually housed in gestation stalls (n = 475). For 140 individually-housed and 330 group-housed sows, backfat depths at the P2 position were determined using A-mode ultrasonography at gestation days 55 to 60, at farrowing, and at weaning.
Results: Group-housed sows were involved in more aggressive encounters than stall-housed animals (P < .05). Aggressive encounters per hour were more numerous in grouped sows during feeding on day 3 than during the day of grouping (P < .001). Salivary cortisol concentrations were higher in grouped sows, but differences between pre-and post-relocation concentrations were not correlated with levels of aggression. There was no effect of housing on backfat depths or sow fertility.
Implication: If sows are grouped during gestation, particular attention should be directed toward feeding management to avoid excessive aggression and possible adverse effects on welfare.
