Digestive efficiency of the growing rabbit according to restriction strategy and dietary energy concentration
Résumé
Post-weaning restriction strategies are used in French rabbit breeding systems to improve the health status, the digestion and the feed efficiency. However, this effect could be affected by the dietary chemical composition. Thus, we aimed to study the digestive response of the growing rabbit according to a 2x2 experimental design: the intake level (free=100 vs limited to 80% of the free intake) and the digestible energy "DE" concentration of the diet (control "C" or high "H"). Four groups of 12 rabbits were housed individually in metabolism cages and allotted at weaning (35 d) to four treatments: C100, C80, H100, H80. The C and H diets were formulated to differ by 16% for their DE content (9.69 vs 11.24 MJ DE/kg as fed resp.), by substituting starch to lipid (141 vs 91 g/kg and 19 vs 72 g/kg), while their NDF level was similar (337 vs 345 g/kg). Animals were fed the experimental diets from 35 to 70d old. For C80 and E80 groups the intake was limited during four weeks after weaning. Digestive efficiency was assessed after two weeks of adaptation to the treatments (49-53d). For rabbits fed freely, the energy digestion was 2.2 pts higher for H diet (P<0.05), leading to a DE level of 10.90 MJ/kg (vs 9.71 for C100 group). The protein digestion was improved by 1.7 pts for H diet, because more protein was supplied by soya bean meal. Digestive efficiency of restricted rabbits was higher for all nutrients and for the two diets, but especially for H diet. The energy digestion was 2.7 pts higher for C80 (64.4 vs 61.7% for C100) but 5.3 pts higher for E80 (69.2 vs 63.9% for H100), leading to a significant interaction (P=0.012 for diet X restriction). The digestibility of crude protein was meanly 6.1 pts higher for restricted rabbits (78.7 vs 72.6%, P<0.001) without interaction with the diet. The restriction also improved the NDF digestion by 6pts. In conclusion, the digestion of the growing rabbit was improved when restricted fed, but the extent of this effect depends of the dietary composition.