Effects of Age and Dietary Fibre Level on Caecal Microbial Communities of Conventional and Specific Pathogen-Free Rabbits

Caecal community structure in conventional and specific pathogen-free (SPF) rabbits was assessed by performing dot-blot hybridization with 16S rRNA targeted oligonucleotide probes. The variation of the caecal flora was analysed according to age (18-70 days old), nutritional status (acid detergent fibre=19% in standard and 9% in fibre-deficient diet) and rabbit health (healthy vs diarrhoeic). Caecal flora was stabilized at around 25-28 days. Bacteria and archaea represented 73% and 22%, respectively, of the total microbial communities at weaning (28 days). Cellulolytic bacteria ( Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and F. intestinalis ) represented <7% of total bacteria, with a predominance of R. flavefaciens and R. albus, respectively, for conventional and SPF rabbits. Bacterial and archaeal rRNAs were twofold higher in conventional than in SPF rabbits, fed standard diet ( p <0.001). In conventional rabbits, archaeal community was twofold higher with standard diet than with fibre-deficient diet. In both types of rabbits, quantities of Flexibacter-Cytophaga-Bacteroides rRNA were twofold higher with fibre-deficient diet than with standard diet. In diarrhoeic conventional rabbits, the proportion of eukaryal rRNA increased 4-fold, but proportions of bacterial and archaeal rRNA decreased by 1-, 2- and 6-fold, respectively. The quantities of rRNA of F. succinogenes and F. intestinalis in conventional rabbits were, respectively 17 and 5 times higher in sick than in healthy animals, and decreased by 7-fold for R. albus. This study shows some microbial interactions according to nutrition and health of the rabbit.