Effects of group size and cage enrichment on social behaviour and skin injuries of breeding rabbits housed part-time in group.

Housing of breeding does in group pens can result in skin injuries and stress due to maternal protective behaviour and hierarchy fights. Aggression can be partly reduced by using single-litter cages during the first weeks of the reproductive cycle and by delaying the grouping of does with their litters until the kits are older. Hierarchy fights do still occur in these part-time housing systems, however. The present study evaluated the effect of group size and cage enrichment on doe and kit skin injuries and on doe social behaviour. During four cycles, groups of either three or four does with their 22-day-old kits were housed in group pens for 13 days. Pens were assigned one of the following treatments (n = 12 pens per treatment): group of four does with no additional enrichment, four does with additional cage enrichment, three does with no additional enrichment and three does with additional cage enrichment. Cage enrichment was comprised of plastic pipes and elevated platforms. As pen size remained constant, a change in group size also implied a proportional change in stocking density. The number and severity of skin injuries were monitored before grouping and at 1, 3, 6, 9 and 13 days after grouping. Video recordings from all group pens were scored continuously for doe behaviour during the first 24 h after grouping in the first and second reproduction cycle and for the first 8 h in the third cycle. Four severely injured does needed to be removed after grouping. During the first day after group housing, respectively, 72.6 and 13.0% of the does and kits acquired at least one new skin injury with respect to the onset of group housing. Compared with groups of four, does in groups of three had lower averaged skin injury scores (9.41 versus 8.40, P = 0.004). Of all observed postgrouping social behaviours, submissive behaviour was most frequently observed (42.8%), followed by aggressive behaviour (29.8%), engaging behaviour (25.1%) and non-aggressive social contact (2.3%). Does used the enrichment during 11.1% of the total observation time, during which the platforms were more frequently visited (97.2%) in comparison to the plastic pipes (2.8%). As shown by the percentage of injured animals on the last day of grouping (does: 61.9% and kits: 18.4%), postgrouping aggression remains a problem that appears difficult to reduce to acceptable levels by reducing group size (and stocking density) or by providing cage enrichment.