HEALTH, WELFARE, AND PRODUCTIVITY OF PIGS HOUSED UNDER SPECIFIC-STRESS-FREE CONDITIONS IN COMPARISON WITH 2-SITE SYSTEMS

This study describes the effects of housing pigs under optimal climati c conditions in a Specific-Stress-Free (SSF) housing system on health, behavior, immunological responsiveness, and production performance of 78 pigs from 10 litters. Pigs housed in an SSF system, where they wer e neither mixed nor transported, were compared with a control group of pigs for which transport was simulated and which were mixed at approx imately 25 kg; transportation to another location and mixing are usual procedures in two-site systems. The SSF pigs had a higher growth rate for the finishing period (P < .01), but this was a smaller improvemen t in performance than in previous studies, probably due to less mixing in this study. Clinical signs were hardly seen in the SSF group, but aggression after mixing caused ear lesions in the control group. Pigs that were not mixed had a higher response 12 and 18 h after an intrade rmal injection of phytohemagglutinin (P < .001) compared to the contro l pigs. At 1 d and 1 mo after mixing the control pigs, more agonistic interactions were seen in these pigs compared with the SSF pigs (P < . 05 and P < .01, respectively). In conclusion, health, welfare, and pro duction performance of pigs are improved when pigs are kept in an SSF housing system where they are not mixed or transported.