Effect of cage floor and stocking density on growth performance and welfare of group-housed rabbits

Two hundred forty rabbits weaned at 36 d (LW=1103±41 g) were housed in groups to evaluate the effect of stocking density and type of cage floor on behaviour, health status, growth performance, and carcass and meat quality. The rabbits were put in groups of 6 into 40 cages of two sizes (78 x 64 cm or 58 x 64 cm) corresponding to two stocking densities (D12, 12.1 rabbits/m2 vs. D16, 16.2 rabbits/m2). Within density, four types of floor were compared (steel slat, plastic slat, wire net and straw litter on wire net) according to a 2 x 4 factorial arrangement with five replications (cages). The rabbits were fed a unique diet (CP: 15.8%, ADF: 19.3%, DE: 9.8 MJ/kg). No antibiotic was added to feed or water. Rabbit reactivity was assessed by the tonic immobility and open-field tests at 70 and 74 d of age. Rabbits were slaughtered at 78 d to evaluate carcass and meat quality. Femur dimensions and resistance to fracture were measured. Sanitary status and growth performance were highly satisfying in all treatments: growth rate averaged 45.5 g/d and final weight 2967 g, with a feed conversion rate of 3.49. Stocking density did not affect growth performance, meat quality, nor animal reactivity. In contrast, the type of floor significantly affected growth performance: rabbits kept on straw bedded floor showed the lowest final weight (2865 g vs. 3000 g on average, P=0.03), weight gain and feed intake. Differences in carcass and meat quality mainly depended on the weight at slaughter: dressing percentage and separable fat of the carcass were lower (P<0.01) in the lightest rabbits kept on straw (58.6% and 2.3%, respectively) compared to the heavier animals of the other three experimental groups (average values 59.9% and 3.0%, respectively). The type of floor also affected animal reactivity: the number of attempts necessary to induce immobility, considered inversely correlated with fear towards humans, was lower in rabbits kept on straw; these rabbits also showed a more passive reaction during the open field test, spending less time exploring and more time in an immobile state (P<0.01) in comparison with the animals housed in the cages with plastic slat or wire net floors.