Biochemical and Microscopic Comparison of in vivo and in vitro Rumen Fermentations3

Abstract

A comparison of in vivo with in vitro cellulose fermentation by rumen micro-organisms was undertaken, based on rate of fermentation (as measured by volatile fatty acid production and the nylon bag technique), quantitative identification of end-products of fermentation and microscopic examination of bacteria. The rates of cellulose digestion and production of volatile fatty acid end-products in the in vivo and in vitro fermentations were similar under the conditions used in these experiments. Gram-negative micrococci, which were found in large numbers in vivo, proliferated in vitro and in vivo on purified cellulose. When mixed hay was used as a substrate both in vivo and in vitro, fermentations could be carried out in vitro for periods of 24–30 hours without any marked morphological change in the bacterial population.