Effect of group size and escape enrichment on reproductive performance of breeding does in part-time group housing

Societal demands for group housing of social farm animals such as rabbits are increasing due to animal welfare concerns. When breeding does are housed in groups, maternal protective behaviour negatively affects the reproductive performance of the does. In part-time group housing, does are housed in single-litter cages starting shortly before parturition until the first part of lactation and then group housed for the second part after their protective behaviour has diminished and the kits are more resilient. The aim of this study was to evaluate the reproductive performance of breeding does in a part-time group housing system with provision of escape enrichment and different group size (and concomitant different stocking density, as pen size remained unchanged). For each of the four consecutive reproductive cycles, 42 does with their kits switched at 22 d post-partum (pp) from single-litter to group housing for a total period of 13 d in pens of 200×102 cm by removing walls between four adjacent single-litter cages. Newly created group pens (N =12 pens per treatment) varied in group size, stocking density and enrichment: groups of either three or four does were divided over same-size pens with or without escape enrichment (2×2 factorial design). The escape enrichment was comprised of two sets of PVC pipes and two extra elevated platforms. Does were weighed and kits counted at parturition, after which kits were cross-fostered. Kits were counted and weighed again 22 and 35 d pp. Results for mean doe fertility (90.0%), number of kits (9.1 kits/litter) and kit weight (1037.3 g/kit) at weaning were comparable with professional farms using single-litter cages. No significant effects of group size and escape enrichment were found for any of the reproductive parameters. While housed in group, seven does were removed from the experiment, from which four does were severely injured. Post-grouping kit mortality was rather low (6.7%), but three kits were euthanised due to severe injuries. In conclusion, provision of escape enrichment and altered group size (and stocking density) had no profound effect on the reproductive performance of part-time group housed does.