THE EFFECT OF WEANING DIET ON THE SUBSEQUENT COLONIC METABOLISM OF DIETARY FIBER IN THE ADULT-RAT

The effect of the weaning diet on the subsequent colonic metabolism of bran and pectin in the adult rat has been investigated. Feeding a fibre-reduced diet on its own or supplemented with bran (WB) and pectin (P) from weaning (fibre-reduced (weaning)) was compared with introducing the same diet to age-matched rats reared on a standard laboratory diet from weaning (fibre-reduced (6 weeks)). The effects of the diets on colonic metabolism were measured by wet and dry caecal contents and stool weights, caecal sac weight, and caecal and faecal short-chain fatty acids (SCFA). Final body-weights were greater for fibre-reduced (6 weeks) and fibre-reduced (6 weeks) + P groups, but not fibre-reduced (6 weeks) + WB, than those of the fibre-reduced (weaning) rats. Rats fed on fibre-reduced (6 weeks) diet had a higher total caecal SCFA content than fibre-reduced (weaning) control rats. Fibre-reduced (weaning) + P-fed rats had a threefold higher caecal concentration of both propionate and butyrate than the matched fibre-reduced (6 weeks) + P group. Fibre-reduced (weaning) + WB animals had a significantly higher butyrate caecal concentration compared with their matched fibre-reduced (6 weeks) + WB group. Fibre-reduced (weaning) + P-fed rats had a lower faecal output than the fibre-reduced (6 weeks) + P rats. There was no difference in faecal output in rats fed on either fibre-reduced (6 weeks) + WB or fibre-reduced (weaning) + WB. The faecal concentration of SCFA was in general higher in the rats fed on fibre-reduced (weaning) alone, + P, or + WB than in those fed on fibre-reduced (6 weeks) alone, + P or + WB. Faecal output of total and individual SCFA was increased on the fibre-reduced (weaned) + WB diet compared with fibre-reduced (6 weeks) + WB-fed animals. The diet at weaning may be important in determining the pathways of caecal bacterial metabolism in the adult rat. In studying the effect of a dietary fibre on caecal metabolism and faecal output, when the diet is changed appears to be important.