Abstract
When ground concentrated feed (10% w/v) was incubated in an artificial rumen with a ruminal microbial population from a hay-fed sheep, large amount of lactate accumulated after a short period (2 hr). On the contrary, with a population from a hay-concentrate fed animal, normal volatile fatty acid production was observed under the same conditions, and, although lactate accumulated at the early phase of incubation, it disappeared later. Removal of protozoa from these populations gave similar features with respect to the fermentation products. Accumulation of lactate at the later phase of incubation (4-6 hr), which was due to the activities of newly proliferated diplococcus- and streptococcus-type bacteria, occurred with both populations when the ratio of the concentrate to cell density became larger. The rate of glucose consumption of the hay-concentrate population at the initial phase was 5 times larger than that of the hay population. These results suggest that the increased capacity of sugar assimilation of the hay-concentrate population as compared to that of the hay population might prevent lactate accumulation at the later period by repressing the multiplication of lactate- forming bacteria by keeping concentration of easily fermentable carbohydrates at low levels.
