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. flaefaciens, Fibrobacter succinogenes and F. intestinalis) represented 7 % of total bacteria, with a predominance of R. flaefaciens 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 (p0.001). 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 t