CONSEQUENCES OF REDUCED FIBER INTAKE ON DIGESTION, RATE OF PASSAGE AND CECAL MICROBIAL ACTIVITY IN THE YOUNG-RABBIT

The present work was undertaken to study in vivo fibre degradation, ra te of passage and caecal fermentation activity (CFA) in the young rabb it (7 weeks old) receiving ad lib. a control (C) or a low-fibre (LF) d iet (400 and 220 g neutral-detergent fibre (NDF)/kg respectively), As a consequence of the 50 % reduction in the dietary fibre level, the vo luntary food intake of the rabbits decreased by 25 %, and the daily fi bre intake was reduced by 60 % (26.7 and 10.8 g NDF/d for groups C and LF, respectively), In spite of a longer mean retention time of the fi bre particles, the quantity of fibre digested daily was significantly lower (P < 0.01) for the LF than for the C group (4.0 and 7.8 g NDF/d respectively), The circadian distribution of the faecal excretion (as a percentage of the total DM output) did not differ between diets (P = 0.52) and no interaction was found (P = 0.96) between diet and time o f excretion, Also, variables describing the CFA showed no interactions between diet (C or LF) and time of sampling (during caecotrophy or du ring hard faeces excretion). Our results indicated no direct relations hip between the quantity of fibre digested and the total short-chain f atty acid concentration in the caecum, but the fermentation pattern in dicated lower proportions of acetate for the LF diet, Higher levels of diaminopimelic acid (DAPA) and ATP were found for the LF diet associa ted with an improved dietary fibre digestibility, suggesting a higher microbial activity, However, this effect was balanced by a lower caeca l digesta turnover rate and the microbial biomass output estimated thr ough the faecal DAPA output did not vary significantly.