Nutritive value of different pastures and soil intake in free-ranged organic growing rabbit
Abstract
Free-ranged organic rabbit correspond to the consumer’s demand of improved animal welfare conditions but lacks in technical reference values. Moreover, the risk of exposure to environmental contaminants of rabbits in these conditions has to be evaluated by an estimation of soil intake. Therefore, 30 growing rabbits have been enrolled (from weaning at the age of 43 days to slaughter at day 100) in two groups of 5 movable cages on two pasture types: sainfoin or fescue. Each cage contained 3 animals and had a shelter of 0.4 m2 and an pasture surface of 1.2 m2. The cages are moved daily on the pasture. A commercial pelleted organic feed was daily given at a level of 64 g/animal. Grass intake was evaluated by the difference between offered and residual grass (cut over 3 cm). Soil intake was estimated by an internal marker method and dry matter digestibility measure. Therefore, concentrations of acid insoluble ash were analysed in soil, all components of diet (i.e. vegetation and feed) and faeces. Moreover, digestibilities on pasture were compared with digestibilities of the same pelleted feed, both vegetation types and their mixtures were determined in indoor ‘controlled’ conditions. Pelleted feed was totally consumed and the pasture dry matter (DM) intake averaged 55 g (from age of 43 to 100 d) without difference between sainfoin or fescue plot. The rabbit growth was half-higher on sainfoin compared to fescue plot (29.3 vs 20.0 g/d, P<0.05). The digestibility of fescue varied from 37 to 43% for pasture and indoor measurement respectively, while that of sainfoin was stable (65.5 to 66.5 respectively). The fescue-feed mixture had a DM digestibility of 37 and 47% in indoor and pasture trial, while for sainfoin-feed mixture digestibility were respectively 65.3 and 61.7. Soil intake was lower (P<0.01) on fescue (1.3% of total DM intake or 1.9 g/d) compared to sainfoin pasture (3.0% or 4.2 g/d). The lower soil intake on fescue pasture could be due to the better soil cover by grass forming a buffer between animals and soil in comparison to sparser sainfoin cover.