Alternative pen housing system for fattening rabbits: effects of group density and litter

Purpose of this experiment was to verify the compatibility of a group housing system, from weaning to slaughter, with the rabbit modern productive standards, evaluating the effects of different stocking densities and type of litter on health, performances and some aspects of carcass and meat quality. Two single experiences were carried out: a first, where 184 rabbits were housed in two-place cages or in pens on a straw litter at different densities (8 or 16 rabbits per m2); a second, where 232 rabbits were housed at the same densities on straw or on wood shaving, while the control group was traditionally housed in cages. In trial 1, mortality rate was significantly higher for rabbits bred on litter at the higher density (15.6% vs 4.2% and 7.5% for groups housed on litter at low density or in cages, respectively). Higher death incidence was mainly due to coccidiosis. Thus, a prophylactic treatment was provided to all the animals before the beginning of trial 2 resulting in a lack of differences in mortality rate among the groups. If rabbits housed in cages showed a significantly higher weight increase and a better feed efficiency than rabbits housed on litter in trial 1, final live weight, daily weight gain and feed to gain ratio for caged animals were not significantly higher than for rabbits housed on litter in experiment 2. However, growing performances for rabbits kept at lower density were significantly higher than for the other animals reared in pens (P<0.05), while the type of litter had no effects. Animals caged showed a carcass weight and dressing out percentage significantly higher than all the other groups in the first assay. Furthermore, the hot carcass weight among rabbits housed on litter was significantly higher for lower stocking density. In experiment 2, carcass weight turned out to be higher for rabbits in cage than on litter at the highest density while dressing out percentage was better than all the other experimental groups (P<0.001). Moreover, carcass weight was significantly higher in rabbits kept at lower density than the others ones reared in pens (P<0.05). The full gastrointestinal tract was significantly heavier in rabbits housed in pens on straw litter, in comparison with the caged animals. The chemical composition of the caecal content however did not show variation of the fibre composition as a function of the litter type. In trial 1, the pH at 45 min and at 24 hrs post mortem, as well as meat colour parameters were the same in all experimental groups. In experiment 2, it can be observed that the hind leg weight was constant among the groups, while the muscle to bone ratio of the cut was significantly higher in caged than in all the other animals. Furthermore, rabbits on litter had on the whole meat with an higher water and a lower lipid content. In conclusion, group housing system on litter imply some relevant questions that have to be pointed out, particularly concerning pathology problems (mainly connected to coccidiosis) compared to the intensive breeding in cages. Growth performances, slaughter results and carcass quality are on the whole better for animals traditionally caged.[...