Role of fibre in rabbit diets. A review

The effect of fibre on rate of passage, control of gut flora, caecal fermen tation, and performance of rabbits has been reviewed. Both physical and che mical characteristics of fibre affect these variables. An increase of the p roportion of fine particles (< 0.315 mm) increases NDF digestibility, acidi ty and weight of caecal contents, fermentation time and microbial protein r ecycled through caecotrophy, but decreases rate of passage and intake. A mi nimal proportion of large particles (> 1.25 mm) is also required to allow a n adequate turnover rate of caecal contents, and then to maximise microbial efficiency. The fraction of pectin components (arabinose, galactose and ur onic acids) of cell walls accounts for most of the total fibre digestibilit y. An increase in the dietary concentration of these constituents leads to an increase of acidity of caecal contents and microbial protein recycled th rough caecotrophy. Dietary lignin content is negatively related to energy d igestibility and also to the accumulation of digesta in the caecum. Both ex cessive and insufficient dietary fibre levels lead to an impairment of rabb it's performance. Practical recommendations on optimal fibre concentrations and minimal proportion of large particles are given for breeding does, fat tening rabbits and mixed diets. (C)Elsevier/Inra.