Effect of environmental enrichment and group size on behaviours and live weight in growing rabbits

The aim of this research was to study the effects of group size and environmental enrichment on behaviour and growth of 108 hybrid growing rabbits (Oryctolagus cuniculus). We compared the behaviour (time budget and reactions to specific behavioural tests: "tonic immobility" and "emergence test") and live weight of growing rabbits housed in cages with a different number of rabbits per cage (2, 3 and 4; same density: 14 rabbits/m(2)). Half of the cages were enriched with a wooden stick (cylindrical Robinia Pseudoacacia, 20 cm of lenght and 6 cm of diameter) hanging from the ceiling of the cage. The stick and number of animals per cage had no effect on weight gain or on behavioural tests responses. Interaction with the stick was significantly higher at the beginning of the growing period. Principal component analysis performed on the data for the whole period showed significant differences according to the treatments: increasing the number of rabbits per cage and introducing a wooden stick seemed to affect locomotor activity frequency and social interactions. Rabbits housed 3 and 4 per cage showed less lying behaviour and higher locomotor activity and sitting. The larger functional space allowance enabled rabbits to perform more natural behaviours compared to smaller cages (2 rabbits/cage). Environmental enrichment seems to be related to higher allogrooming behaviour frequency, which could indicate a social behaviour related to pheromonal olfactory stimulation and mutual recognition.