Cage enrichment to minimize aggression in part-time group-housed female breeding rabbits.

In most rabbit farms, breeding does kindle and nurse their kits in single-litter cages throughout their entire reproduction cycle. However, the protective behavior can lead to aggressive displays and injuries when the does are housed in groups. This study aimed to evaluate cage enrichment for reducing the agonistic behavior in part-time group-housed does. A total of eighty does with their 22-day-old kits were allocated to 20 multi-litter cages, with each cage housing four does and their litters for 10 days. Each multi-litter group was subjected to one of four treatments: alfalfa blocks as distraction material (A), wooden panels underneath the platforms (P), both alfalfa and wooden panels (AP), or no extra enrichment (controls, C). This experiment was replicated for three consecutive reproduction cycles. The skin injuries of the does and the kits were scored with a tagged visual analog scale before grouping and at one, three, six, eight, and 10 days after grouping. Computer vision techniques were used to continuously monitor rabbit activity and agonistic behavior (aggression and fleeing/chasing) during the first 24 h after grouping, specifically during light hours. During the first day in the group, 67.2% of the does and 13.4% of the kits acquired new injuries. This increased to 82.0 and 33.2%, respectively after 10 days in the group relative to the onset of grouping. The injury scores of the does increased toward the sixth day after grouping compared to the first (p < 0.001) and were highest on the tenth day for the kits (p < 0.001). On all the observation days, the number of injured does was higher in C compared to A (p = 0.04) and AP treatment (p = 0.005). There were no other treatment effects observed on the doe or kit skin injuries. Rabbit activity was highest after grouping but decreased after the first and second days (p < 0.001). The agonistic interactions between the does involved more fleeing/chasing behavior (62.0%) rather than aggression (38.0%). Although hierarchy fights are likely when unacquainted does are group-housed, the many animals that sustained injuries and the high injury scores confirm that part-time group housing for does is challenging and possibly inevitable. This study has shown that alfalfa, with or without wooden panels, can slightly reduce the number of injured does.

Quantifying agonistic interactions between group-housed animals to derive social hierarchies using computer vision: a case study with commercially group-housed rabbits.

In recent years, computer vision has contributed significantly to the study of farm animal behavior. In complex environments such as commercial farms, however, the automated detection of social behavior and specific interactions between animals can be improved. The present study addresses the automated detection of agonistic interactions between caged animals in a complex environment, relying solely on computer vision. An automated pipeline including group-level temporal action segmentation, object detection, object tracking and rule-based action classification for the detection of agonistic interactions was developed and extensively validated at a level unique in the field. Comparing with observations made by human observers, our pipeline reaches 77% precision and 85% recall using a 5-min tolerance interval for the detection of agonistic interactions. Results obtained using this pipeline allow to construct time-dependent socio-matrices of a group of animals and derive metrics on the dominance hierarchy in a semi-automated manner. Group-housed breeding rabbits (does) with their litters in commercial farms are the main use-case in this work, but the idea is probably also applicable to other social farm animals.

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.