Effect of inulin supplementation and age on growth performance and digestive physiological parameters in weaned rabbits

[EN] Three diets were formulated, a control diet (C, 40.7% NDF, 15.1% CP), the same diet but medicated (M, 500 mg/kg oxytetracycline and 50 mg/kg thiamulin), and a third diet obtained substituting 4% of barley with inulin (Frutafi t) in C diet (I). Pannon White does and their litters were randomly allocated into three groups (8/group) at 21 d of lactation and diets offered to the does and kids from 21 d of lactation onwards. After weaning (28 d), growing rabbits (30 cages/ treatment, 2 rabbits/cage) were fed the same diet as before weaning. At 28, 35 and 42 d of age, 6 healthy animals from each group (1 animal/cage) were slaughtered. Live body weight, feed intake and feed conversion ratio increased and growth rate decreased with age (P<0.001). Feed intake decreased in rabbits fed I diet compared to those fed M diet (by 11%, P<0.05), with those fed C diet showing an intermediate value. Growth rate from 28 to 35 d of age was not affected by diets, but decreased from 36 to 42 d in rabbits fed I diet compared to those fed C and M diets (P<0.05), with no effect on feed conversion ratio. Inulin did not affect mortality, which was low (¿ 3.3%), but increased morbidity compared to C and M diets (11.7 vs. 2.5%, P<0.05). Diets did not affect caecal weight, pH, cellulase and pectinase activity or microbial counts. Inulin diet decreased caecal xylanase activity (P<0.05) compared to C and M diets, reduced propionic and butyric acid and increased acetic acid concentration compared to M diet, whereas C diet showed intermediate values. Caecal pH and counts of E. coli and total aerobic bacteria increased and pectinase activity decreased (P<0.05) at 35 d of age (compared to 28 and 42 d of age). The number of the strictly anaerobic bacteria decreased and cellulase and xylanase activity increased (P<0.05) at 42 d of age compared to 28 and 35 d. Propionic acid concentration decreased with age from 28 to 42 d (P