Microbial activity in the caecum of the rabbit around weaning: impact of a dietary fibre deficiency and of intake level

Abstract

The current study was designed to evaluate the caecal microbial activity in the young rabbit, as influenced by dietary fibre concentration and feed intake level. Caecal fermentative activity and bacterial fibrolytic activity were measured before and after weaning (28-day old) in young (six litters of eight per diet) fed before weaning a fibre deficient diet “DF” (92 g acid detergent fibre (ADF) kg −1), or a standard fibre diet (165 g ADF kg −1) containing either a standard (diet SF) or an excessive methionine level (diet MSF). The effect of the dietary fibre level on microbial activity was evaluated by comparing DF and SF groups. The fibre effect itself, without change in intake level, was estimated by comparing DF and MSF groups, since a high level of methionine reduces the intake level in rabbits. Feed intake (from 28 to 42 days) was 13% lower for MSF than for SF group, but was similar to DF group. Between 21 days of age and weaning, caecal volatile fatty acid (VFA) concentration doubled and then slightly increased until 42 days of age. A linear reduction for propionate and, conversely, an increase in butyrate molar proportions were observed with age. Until weaning, VFA concentrations were similar between the three diets, although it tended to be lower for DF ( P=0.067). Subsequently, VFA concentration of SF group increased, while for DF it decreased (respectively, 72 mM l −1 versus 40 mM l −1 at 42 days, P<0.05). Pectinase, xylanase and cellulase activity of bacteria increased by 80% between 25 and 34 days of age. The bacterial fibrolytic activity was not significantly affected by the reduction of the intake (MSF versus SF), while fermentative parameters of MSF group were intermediate between SF and DF, suggesting that fibre effect partly depended on the intake level.