Results of rearing and growing 3250 piglets derived from 287 litters of 99 German Landrace sows in parities 1-11, from parturition throughout 5 weeks post-weaning, were compared in two farrowing systems. The Group-Farrowing System (GFS) was designed according to natural behaviour of wild pigs and contained 8 farrowing boxes allowing sows and their litters to move freely on an area of 85.2 m(2). In contrast, the Single Farrowing System (SFS) was a pen in which sows and their litters were housed individually and could move freely on a restricted area of 6.7 m(2). Sows were only fixed during farrowing. The first experiment with a suckling period of 35 days comprised 98 litters from 60 sows (parities 1-4). The second experiment with a suckling period of 28 days involved 189 litters of 70 sows (parities 1-11). In experiment 1, body weight of GFS-piglets was significantly higher by 4.57 kg (19 %) at the age of 70 d compared with SFS-piglets. In the second experiment, the proportion of stillborns was significantly lower by 50 % in GFS than in SFS. Furthermore, body weight of GFS-plglets showed a greater homogeneity during the first 35 cl of life than that of SFS-piglets. In SFS, a positive correlation between parity of the sow and stillborn rate was observed. Behavioural studies in both experiments revealed that GFS-piglets, reared during the suckling period in close contact to other sows and piglets from other litters, were in a better condition at weaning than SFS-piglets. Comparisons with other GFS-types show that the success of farrowing in grouphousing is dependent on the type of housing conditions, in particular on the possibility for sows and piglets to live according to their specific behavioural repertoire. The factors critical in this context are discussed.
