A FIELD-STUDY ON GROUP HOUSING OF LACTATING SOWS WITH SPECIAL REFERENCE TO SOW HEALTH AT WEANING

Four farms that group-housed sows from 2 weeks of lactation until wean ing (G-farms) and 3 farms that kept the sows individually penned throu ghout the 5 to 6-week-long lactation period (C-farms), were compared i n terms of sow health. All sows were crossbred Swedish Yorkshire x Swe dish Landrace. The daily food ration was similar on all farms except d uring the group-housing period, when G-farm sows were fed ad libitum. Sows were grouped in the breeding section and kept grouped on deep lit ter in the dry sow section on all farms. Individual health examination s were performed at the time of weaning (+/- 4 days) on 179 G-farm sow s and on 167 C-farm sows. Teat- and udder skin wounds occurred less fr equently (p < 0.001) in G-farm sows than in C-farm sows. In addition, preweaning atrophy of all mammary glands occurred in 6.6% of the G-far m-sows but not in a single C-farm sow (p < 0.001). This indicates that sow-piglet interactions decrease when sows are group housed. However, these differences did not occur in primiparous sows, suggesting that the relation between the primiparous sow and her litter is not affecte d. Mastitis frequency was the same in the 2 systems. Moreover, the fre quency of locomotor disorders was the same in the 2 groups, and hoof o vergrowth was common in both systems. These similarities could be due to the fact that all farms group housed dry sows on deep litter. A str ong relation (p < 0.001) between hoof overgrowth and locomotor disorde rs was evident. Low access to food due to low rank among primiparous g roup-housed sows was indicated by a lower (p < 0.05) backfat thickness compared with multiparous sows, and a higher (p < 0.001) frequency of skin wounds compared with individually housed primiparous sows.