Effect of dietary supplementation with purified cellulose in isoenergetic diets on performances, caecal fermentation, and gut microbiota of growing rabbits
The primary dietary component for rabbits is fiber, which ensures the normal functionality of their digestive systems and controls the diversity and composition of their microbial communities. The health of the rabbits is therefore influenced, which has an impact on feed intake, feed conversion ratio, and overall farm productivity. By increasing insoluble fiber and using purified cellulose and increasing the energy content of diets by adding fat, the current study tested diets formulated to maintain rabbit digestive health and restrict feed intake, and, consequently, feed conversion ratio. The impacts on the composition of the gut microbiota and the caecal fermentation, besides, diet digestibility and rabbit performance were examined.  Sequencing results showed that the microbial diversity and the bacterial community structure of hard feces barely differed from that of caecal content (P> 0.05). As for the diet effect, no differences in alpha and beta diversity of microbiota were detected in rabbits fed the two diets. However, twelve genera, mostly belonging to the family of Lachnospiraceae, increased (Wald test, P< 0.05) in rabbits fed the diet with the inclusion of purified cellulose and added fat. The increase of insoluble fiber reduced the digestibility of the fiber fractions, while increasing protein digestibility according to changes in dietary levels. On the other hand, growth performance was not affected by the dietary treatment. The increase of insoluble fiber and the addition of purified cellulose in fat-added diets did not affect the diet's nutritional value or rabbit performance, where overall farm efficiency was guaranteed. Despite some changes in the fermentation profile at the caecum may indicate a change in microbial pathways rather than composition, no significant effects on the gut microbiota were observed.