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Pastured organic rabbit farming: growth of rabbits under different herbage allowance and quality
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Edité par CCSD ; Wageningen Academic Publishers -
International audience. Organic rabbit farming is developing in France, but growth performances and herbage intake are still slightly documented. Our study aimed to describe rabbit herbage intake under a wide range of grazing conditions and to characterise the factors that control herbage intake and growth. Three trials were performed in winter, summer and spring, using growing rabbits reared in moving cages (0.4 m2 of grazing area per rabbit, 2 groups of 5 cages per season with 3 rab. per cage), to compare two ‘types’ of pasture dominated by legumes (LEG) or grass/forbs (GRF). Each trial began at weaning (45 d old) when rabbits were transferred to moving cages, and ended at slaughter (100d old), and they received 60 g/d/rabbit of a complete pelleted feed. Mean herbage allowance was 27% higher in LEG (62.3 g DM/kg metabolic weight (MW), equal to kg0.75) than in GRF (49.2 g DM/kg MW). For both pasture types, herbage intake was logarithmically related to herbage allowance and plateaued around 75 g DM/kg MW. Mean total intake was 70.3±19.5 g DM/kg MW, of which half was pelleted feed. Crude protein (CP) and digestible energy (DE) and intake differed by pasture type and season. Mean CP intake was 50% higher in LEG (15.0 g/kg MW) than in GRF (10.7 g/kg MW). In summer, mean DE intake was 27% higher in LEG than in GRF but no significant differences in DE intake were found between LEG and GRF in winter and spring. Maximum DE intake plateaued near 1000 kJ/kg MW. Daily weight gain was always higher for rabbits grazing LEG (mean=22.6 g) than GRF (mean=16.0 g). CP intake was significantly related to weight gain, while DE intake had no significant relations. Meeting the objective of mean daily weight gain of 20 g requires herbage intake of 32 and 50 g DM/kg MW in LEG and GRF, respectively. Therefore, according to the herbage use efficiency observed in our experiments, herbage allowance must reach 41 and 76 g DM/kg MW in LEG and GRF, respectively. When herbage allowance is lower, rabbits cannot meet the CP intake (13 g/kg MW) required for the weight gain objective.
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