Effect of a high fibre intake on the resistance of the growing rabbit to an experimental inoculation with an enteropathogenic strain ofEscherichia coli

Abstract

AbstractResponse to an experimental infection with an enteropathogenicE. coliO103 strain (EPEC) was assessed in growing rabbits given a high or a low dietary fibre diet (200 and 120 g acid-detergent fibre per kg respectively for high ‘HF’ or low ‘LF’ fibre diet). The two experimental diets, differing in fibre level but not fibre quality, were given ad libitum from 21 days of age to two groups of 12 litters of nine pups, weaned at 28 days (trial 1) and caged collectively. At 42 days of age, the two groups were divided in two subgroups (i.e. four groups of 18 animals), inoculated or not with an EPEC O103 strain. Two further groups of 48 rabbits (trial 2) were given LF and HF diets from 28 days (weaning) to 70 days, and were individually housed to control precisely the food intake. Reducing the fibre level led to a lower post-weaning food intake (64 v. 85 g/days in the period from 28 to 42 days of age,P< 0·001) and digestible energy intake (0·75v.. 0·86 MJ/day,P< 0·001), causing a lower growth (proportionately 0·088 lower,P< 0·001). At 42 days of age, only 17% of rabbits had a detectable caecal saprophyteE. coliflora (over 102colony-forming units (CFU) per g, trial 1). Inoculating 6-week-old rabbits with EPEC led to moderate levels of mortality (26%). Health risk index (mortality + morbidity) was numerically higher in LF compared with HF groups (P= 0·12). The acute phase of the colibacillosis was between 3 and 10 days post inoculation. From days 7 to 14 post inoculation, a significantly higher frequency of rabbits having a high faecal excretion ofE. coli(> 105CFU per g) was found in LF than in HF rabbits (respectively 65 v. 26·7%,P= 0·04). The caecal pectinolytic flora reached 108CFU per g at 42 and 65 days of age, and was not affected by diet or EPEC challenge. In 42-day-old rabbits the caecal volatile fatty acid concentration was higher in HF than in LF groups (respectively 79 v. 60 mmol/l,P< 0·05), while the caecal pH was slightly lower (respectively 5·93 v. 6·09,P< 0·01). At 65 days of age, rabbits resistant to the inoculation showed a similar fermentation pattern and fibrolytic flora level to non-inoculated animals. Caecal ammonia level was not affected either by age, diet orE. colichallenge (mean = 12·1 mmol/l). From these results, we conclude that a high fibre intake improved the resistance of the growing rabbit to a specific enteropathy, in association with a higher caecal fermentative activity and lower caecal pH.