The influence of dietary fibre on caecal metabolism in the rat.

The influence of three diets ((1) high-fibre - low-fat, (2) low-fibre - high-fat, (3) commercial breeding diet) on the concentration of short chain fatty acids (SCFA) has been investigated in male and female rats up to 14 weeks of age. Hydrogen was detected in respired gas in all rats with no significant differences between diets or sex. Methane was detected only in control-fed rats at 12 weeks of age and thereafter. Caecal contents contained higher concentrations of SCFA than were found in faeces. There were no significant differences in the total faecal SCFA excreted by rats on the three diets. The proportions of SCFA in the caecum and faeces were influenced by diet. The production and excretion of hydrogen, methane and SCFA in the rat appeared to reflect different aspects of bacterial metabolism. Comparison of caecal and faecal SCFA may indicate differential absorption from the colon or differential metabolism by bacteria or colonic mucosa which may be influenced by diet.