Inoculum for In Vitro Rumen Fermentation and Composition of Volatile Fatty Acids

Abstract

Methods for inoculum preparation were studied to develop a simple in vitro system using large test tubes as fermentation vessels, with a special emphasis on reproduction of the volatile fatty acid composition in the rumen. Rumen contents from sheep fed hay and concentrates were squeezed through two layers of surgical gauze to obtain a liquid and a residue. The residue was resuspended in a mineral solution (2 ml/g) and squeezed again in the same manner. This treatment with a mineral solution was repeated five to nine times. Microbial counting of the squeezed liquids and production of volatile fatty acids by variously combined liquids indicated that the first squeezed liquid contained only a small part of the microorganisms and probably did not represent the population of bacteria and protozoa in rumen contents. When the liquids of the first to sixth squeezings were combined and incubated with carbohydrate sources, composition of the produced volatile fatty acids as well as the acetate/propionate ratios were reasonable and varied in relation to the constitution of the carbohydrate source in the same manner as in the rumen of animals. © 1980, American Dairy Science Association. All rights reserved.