Effects of type and level of fibre on digestive physiology and performance in reproducing and growing rabbits

Abstract

The study aimed to evaluate the effect of level and type of fibre on performance and digestive traits of lactating does and growing rabbits. Two lactation diets were formulated to contain a similar level of NDF (29%): a mixture of alfalfa hay and wheat straw in diet L1 was substituted with apple pulp in diet L2. Three fattening diets were formulated: diet F1 was the same than diet L1 whereas F2 and F3 had higher level of NDF (33 and 36%, respectively) with a mixture of wheat straw and alfalfa hay in diet F2 substituted by apple pulp in diet F3. A total of 110 does and their litters were controlled during two consecutive lactations from 21 to 35 d. At weaning (35 days of age) 480 rabbits were housed collectively (four per cage) and 180 individually. Another 54 rabbits were slaughtered to determine digestive traits at 45 days of age. At 35 days of age, L1 rabbits showed 5.9 and 6.9% higher daily feed intake and body weight than L2 rabbits. In the fattening period (35 to 63 days), L1 rabbits showed a higher growth rate but a lower feed efficiency than L2 animals. In the fattening period, F1 rabbits showed a 5.9% higher weight gain and 8.8% lower feed conversion than F2 animals, whereas animals fed diet F2 had a higher weight gain (7.6%) and a worse feed conversion (6.5%) than animals fed diet F3. The highest apparent ileal digestibility of DM values was obtained for diets F1 and F3. Villi length tended to be longer (P<0.10) in animals fed the diet F1 and F3. No significant influence of treatments was detected on caecal pH, anaerobic bacteria counting or rabbit mortality (only 0.9% on average). In conclusion the substitution of a mixture of wheat straw and alfalfa hay by apple pulp in isofibrous diets increases feed efficiency but also impairs feed intake and growth rate. Furthermore, in a context of low mortality, diets with 29-30% NDF would lead to better performances in the fattening period than diets containing 33-36% NDF levels.