Fibre digestion and rate of passage in the rabbit: effect of particle size and level of lucerne meal

Abstract Faecal digestibility, total and ileo-rectal mean retention time (MRT) were measured on adult female rabbits fitted with a simple cannula at the terminal ileum. Diets given ad libitum contained lucerne meal (LM) as the only source of plant cell walls. Two levels of incorporation and two degrees of grinding for LM were tested: 48.5%, 3 mm; 76.5%, 3 mm; 76.5%, 1 mm. Non-starch polysaccharides in feeds and faeces were measured using gas-liquid chromatography for neutral, and metahydroxydiphenyl colorimetry for acidic surgars. Pectic substances (uronic acids, rhamnose, arabinose, galactose) were highly digested (70%) whatever the diet. Increasing the content of LM resulted in better digestion of glucose and xylose, and in reduction of MRT in the whole tract and in the caeco-colic segment. Reducing fibre particle size decreased cell wall digestion in the rabbit (except for pectic substances), and increased total and ileo-rectal MRT.