A micro-artificial rumen for isotopic experiments.

An artificial rumen for the study of nutrient digestion by the micro-organisms of the rumen was initially developed by Louw, Williams & Maynard (1949). In this, the micro-organisms were contained in a semi-permeable dialysis sac and the diffusible products of digestion removed by a salt solution, the composition of which approximated to that of saliva and which flowed continuously past the outside of the sac. The properties of this type of artificial rumen have been studied by Wamer (1956) and Davey, Cheeseman & Briggs (1960), who suggested criteria for establishing its validity as a functioning system. Warner showed that saline of ionic composition similar to that of rumen liquor gave better results than one equivalent to saliva. Elsden (1952) criticized the use of saline-diluted rumen liquor as a growth medium for rumen microorganisms on the grounds that the population found at the end of the incubation was qualitatively different from that of the original rumen contents. In this respect it is generally believed that many rumen micro-organisms require factors for satisfactory growth which are present in rumen liquor and which, up to now, have been inadequately characterized (Bryant, 1959; Bryant & Robinson, 1961). In the present design these criticisms have been largely nullified by continually perfusing with clear rumen liquor from the same unfed animal. In this way growth factors are maintained in physiological concentrations and soluble, possibly toxic, digestive products never accumulate above a concentration occurring in the rumen liquor. The apparatus is small enough to allow experiments with valuable isotopically labelled compounds. Experiments have been performed with sheep to test the biochemical validity of the artificial rumen and the results compare favourably with the properties of the intact rumen.