The cecal microflora and short-chain fatty acid concentrations were determined in a 4-week trial with Wistar female rats (initial body weight ca. 50g) which were fed standard- or vitamin-free-purified diets containing galactosyllactose (GL). In rats fed the standard purified (SP) diet with a high dose (5%) of GL bifidobacteria, lactobacilli, and anaerobic Gram-positive cocci increased remarkably in number compared with diets containing lactose. Vitamin-free purified (VFP) diets, regardless of the amount (0, 2.5, and 5%) of GL added, resulted in marked increases of the above-mentioned bacteria. In the VFP diet with 5% GL, bifidobacteria and enterococci increased in number, but anaerobic Gram-positive cocci, Bacteroidaceae, and Enterobacteriaceae decreased compared with the 2.5% GL group. Staphylococci decreased in number in the VFP diets containing GL compared with the other groups. In rats fed the SP diets with GL, the total short-chain fatty, acetic, and propionic acids increased in concentration, and n-butyric, iso-butyric, and, iso-valeric acids were reduced. In rats fed VFP diets with or without GL, the concentrations of short-chain fatty acids were greatly reduced compared with the SP diet, but the total and acetic acidsi ncreased in concentration in proportion to the amount of GL in the VFP diet.

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