Effect of the addition of D-xylose on xylanase activity and digestibility of fiber in an artificial rumen.

The effect of adding D-xylose at two different levels as a continuous infusion to an artificial rumen was determined with respect to pH, methane production, volatile fatty acid production, fiber digestion, and xylanase activity. No changes in pH, methane production, or fiber digestion were observed as consequences of increased D-xylose concentrations. Although the propionic acid production was slightly raised on addition of D-xylose, the acetic acid production was lowered to the same extent. A low-xylose infusion increased the xylanase activity by 25%, whereas a high-xylose infusion lowered the activity by 17%. It was concluded that D-xylanase activity was not a rate-determining step in fiber degradation in the rumen.