Does group housing increase the risk of reproduction problems in French sow herds?

The aim of this study was to investigate reproductive performance and possible reproductive problems (late estrus, infertility, reasons for culling) in herds with either group-housed or individually housed pregnant sows. In a second analysis, we evaluated the effects of different group housing systems. Two questionnaires were sent to pig producer organizations in 2009 and 2010 to survey pig farms with group-housed sows. Out of 641 pig farms listed, we kept two subset samples: the first one comprised 256 commercial herds with sow herd reproduction results recorded in the national database in 2009 (group G). Their results were compared to those of a ‘Control sample’ of 256 herds comparable to group G herds in terms of age at weaning, size of the herds and geographic area. We observed few differences in reproductive performance between these two groups. The second sample (n=173 herds) was a subset of G herds for which we had both reproduction data and complete information on housing characteristics and sow management. Feeding system significantly affected several reproduction and longevity criteria, but differences between systems were small. Time of regrouping also impacted sow fertility. Culling due to returns was more frequent in groups with more than 10 sows.