Title: Effect of <i>p</i> H on Population and Fermentation in a Continuously Cultured Rumen Ecosystem
Abstract: The effect of p H on rumen fermentation and microbial population was studied in a continuously cultured rumen ecosystem. A marked decrease in the production of volatile fatty acids and methane from alfalfa hay occurred when the cultures were maintained at p H values below 6.0. The decrease in acetate and methane production was greater than that of propionate production. The culture maintained at p H 6.7 contained the types of bacteria often found in high concentration in the rumen, whereas the culture maintained at p H 5.0 had a high percentage of bacteria which could not be identified with the major rumen bacteria found in rumens of animals fed alfalfa hay. Replacement of the bicarbonate-phosphate buffer used to maintain fermentor p H at 6.7 with phosphate alone did not greatly alter the fermentation products produced from a hay-concentrate substrate.