In Vitro Rumen Fermentation of Alfalfa

A L T H O U G H in vitro and in vivo rumen studies of cellulose digestion and volatile fatty acid production are numerous (Johnson, 1966), a paucity of information is available on the bioenergetics of tureen digestion. From four in vitro fermentations, in which the heat of combustion of substrate and the products was determined, Marston (1948) concluded that the heat of rumen fermentation of purified cellulose was 6% of the combustible energy of the cellulose fermented. More recently, Walker and Forrest ~(1964) incubated whole rumen contents in a novel calorimeter. They found that the rate of heat production of rumen contents 24 hr. after feeding was 1 cal per 1 % solids per 250 ml per hour. The rates of gas and heat production were found to be closely related and directly proportional to the solids contents of the medium. The purpose of this investigation was 1) to develop an in' vitro system in which the energetics of rumen fermentations could be studied and 2) to determine the energetics of alfalfa hay digestion by tureen microorganisms in vitro.