Effect of dietary supplementation with purified wood lignocellulose on performances, caecal fermentation and gut microbiota of growing rabbits

A total of 576 rabbits were housed in 18 open-top elevated pens (32 rabbits per pen) during the fattening period (54-71 d of age) and fed a standard diet or a diet enriched in purified wood lignocellulose and fat formulated to guarantee rabbit optimal digestive health and convenient feed conversion ratio. The impacts on gut microbiota (both hard faeces and caecal content) and caecal fermentation, diet digestibility and rabbit performance were examined. The microbial diversity and the bacterial community structure of hard faeces barely differed from that of caecal content (p > .05). No differences in alpha and beta diversity of microbiota were detected between rabbits fed the different diets. Twelve genera, mostly belonging to the family of Lachnospiraceae, increased (p < .05) in rabbits fed the diet added with the purified lignocellulose and fat. The increase of insoluble fibre by purified wood lignocellulose reduced the digestibility of fibre fractions (NDF digestibility 19.2% vs. 26.8%; p < .001) while increasing protein (73.5% vs. 71.6%; p < .01) and ether extract digestibility. Growth performance was not affected by the dietary treatment (average daily weight gain: 40.9 g/d; feed conversion ratio: 4.04). Total losses (dead + underweight animals) averaged at 4.17% without significant differences between the dietary treatments. In conclusion, the addition of purified wood lignocellulose in fat-added diets did not affect rabbit performance and overall farm efficiency was maintained. Some changes in the caecal fermentation profile may indicate a change in microbial pathways rather than composition, where no significant effects on the gut microbiota were observed.