Changes in the pattern of fermentation in the caecum of rats

Diets promoting fermentation in the caecum and colon are commonly being prescribed as preventatives for colonic cancer (1). Evidence from animal studies indicates that diets promoting high levels of fermentation may not be beneficial to the gastrointestinal tract or immune function. The aim of the current experiment was to examine the difference in fermentation pattern, in terms of volatile fatty acids (VFA’s) and lactic acid, in the hind-gut of rats when fed two different commercial diets and one diet promoting increased fermentation. Thirty six male Wistar rats were fed one of 3 pelleted complete rations (n = 12). Two rations were purchased from commercial outlets, Chow (16.6 MJ ME/kg DM, 22.4 % CP, Ridley Agriproducts), Wheat Based (17.1 MJ ME/kg DM, 19.1 % CP, Breeders Choice Seeds) and one, Rice Based, was formulated to the same specifications as the Wheat Based ration (16.9 MJ ME/kg DM, 18.2 % CP, M. Evans). All rations were fed for 3 hours per day for 11 days. Animals were euthanased for collection of gut contents at either 3 or 21 hours after the time of feeding. Samples of digesta from the caecum, colon and rectum of each rat were collected and analysed for pH and VFA and lactic acid concentration. Data are presented for caecal measurements combined for 3 or 21 hours after feeding. Caecal butyrate concentration (mmol/l) was significantly (P < 0.05) higher in rats fed the Rice Based ration than Chow or Wheat Based rations. The higher concentration of butyrate in the caecum and rectum (data not shown) has previously been thought to be beneficial to the health of the hind-gut in terms of colonic cancer prevention (1,2). However, the concentratio