One week after weaning the rabbit's intestines are almost functionally mature, although the bacterial diversity can still change. Microorganisms populate the whole gastrointestinal tract, but the highest concentrations can be found in the caecum and colon of rabbits. Besides smaller amounts of archaea, yeasts and protozoa, bacteria account for the majority of microorganisms in the intestines of rabbits. In the first two weeks of the rabbit's life the ratio between facultative and obligatory anaerobes is constant. Then Bacteroides dominate the intestinal microbiome followed by Clostridium, Endosporus and Acuformis. Hard and soft faeces generally differ in bacterial composition, particularly in rabbits with less weight. The occurrence of specific bacteria in hard faeces shows a correlation with the weight of rabbits. Obviously feeding has an effect on intestinal microbes. Restricted feeding for a short-time improved intestinal health. Especially dietary fibre seemed to be suitable to prevent gastrointestinal disturbances in young rabbits. Fibre provides the main energy source for bacteria in the intestine of rabbits. The bacteria, which are able to ferment cellulose, xylane and pectin, established themselves with solid feed intake. An early maturation and thus stabilisation of the microbiome seems to be worthwhile in this early stage of life. High neutral detergent soluble fibre with simultaneously low neutral detergent fibre contents in the diet increase the quantity of bacteria. However, other than the known fibre degrading bacteria like Ruminococcus flavefaciens and Fibrobacter succinogenes, are involved in this fibre decomposition.