Use of digestible fibre in replacement to available carbohydrates Effect on digestion, rate of passage and caecal fermentation pattern during the growth of the rabbit

The dietary replacement of available carbohydrates (mainly starch) by digestible fibre was assessed on rabbit growth and digestion. Two diets supplying hemicellulose (diet HC) or a mix of hemicellulose and pectins (HC 1 P) were compared to a control diet having a higher starch content, but a similar content in low digested fibre (lignocellulose ADF 5 155 g/kg). Three groups of 17 rabbits were allocated at weaning (28 d) to each diet. Nine animals of each group were cannulated to follow the caecal microbial activity from 45 to 70 d old. Compared to control, rabbits fed HC or HC 1 P increased feed intake ( 1 10%), but only HC 1 P resulted in a higher weight gain and in a similar feed conversion (mean 2.00), particularly during the postweaning period (4–6 wk old). Transit of liquids was similar among diets, either in the caeco–colic segment or in the whole tract. HC 1 P diet gave short caeco–colic transit for particles (13.1 h), and also the highest caecal SCFA level (62.2 mM/l) and pool (3.8 mM), while HC and control diet led to similar caecal fermentation (mean 5 56.5 and 2.25, respectively for SCFA level and pool). SCFA concentration increased according to the mean intake of ‘‘hemicellulose 1 pectins’’, suggesting that microbial activity and fibre degradation were more affected by the nature of the cell wall than by the caeco–colic retention time.  2000 Elsevier Science B.V. All rights reserved.