We investigated effects of fiber source on absorption of cholesterol in rabbit. Sources of fibers were beet pulp, soybean hull, alfalfa and safflower meal. Cholesterol was added to each feed so that it contains 0.5% cholesterol. The level of plasma cholesterol, total cholesterol and free cholesterol, remained lowest during the period in the rabbits that were fed beet pulp, suggesting that beet pulp was most efficient in interfering with the uptake of cholesterol. The levels of plasma cholesterol in those fed soybean hull or alfalfa meal were high and similar. Fecal cholesterol was highest in rabbits fed soybean hull, and suggesting that soybean hull is very effective to excrete cholesterol. Therefore, soybean hull and beet pulp may be effective in preventing obesity in rabbit.

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Effect of nitrite on the populations of cat intestinal flora was examined. When cat faces were incubated in a growth medium containing glucose, maltose, and, cellobiose, addition of 3 mM nitrite increased lactate production, and decreased the production of propionate, formate, and butyrate. This suggests that nitrite affects the composition of intestinal flora. RFLP (restriction fragment length polymorphism) analysis also showed that addition of nitrite altered the composition of intestinal flora. In the presence of nitrite, the proportions of Enterococcus sp. and Clostridium sp. increased. Then, nitrite-reducing bacteria were isolated from cat feces by successive cultivation in a medium containing nitrite. Based on Gram-staining, shape of cell, characteristics of colony, growth conditions, sequence of 16S rDNA, utilization of carbohydrates, and fermentation products, the isolated bacteria were putatively identified as Clostridium perfringens, Escherichia coli, and Streptococcus bovis. However, putative S. bovis had extremely low nitrite-reducing ability and little nitrite reductase activity. Putative C. perfringens and E. coil had much higher nitrite-reducing ability and nitrite reductase activity. These two bacteria were found at high frequency, which agreed with the result of RFLP analysis. These results suggest that the two bacteria are predominant nitritereducing bacteria in the cat intestine. The amount of nitrite reductase in cells, or ability to reduce nitrite, was different among the strains even within the same species.

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