ABSTRACT
Micro-organisms are now known to be the agents responsible for many important chemical changes in the rumen contents. By the fermentation of polysaccharides they produce large quantities of the lower fatty acids which are absorbed and utilized by the host; they digest a considerable part of the protein in the fodder and resynthesize proteins during their own growth and proliferation; they are capable of converting suitable forms of non-protein nitrogen to protein, and can synthesize many of the vitamins. The accurate assessment of the extent to which such processes take place, however, presents major difficulties—difficulties bound up with the fact that the rumen is a reservoir into which more or less continuous supplies of food, water and saliva enter, and from which some products of the fermentation are absorbed, while others, together with food residues, pass to lower levels of the alimentary tract. As a consequence, the extent to which various compounds are digested, released or synthesized, cannot be determined from the concentrations of these substances in the rumen, and so indirect methods of investigation must usually be applied to such problems.
The residue after extraction with water showed no iodine-staining reaction, and parallel analyses carried through without the starch being dried from ethanol at 70· C. also indicated that this step did not interfere with solution of the starch in water.
Separate tests showed no starch remaining after centrifuging at 17,000 × g.
In experiment no. 6 the animal was fed ad lib. The amount of lignin consumed was not determined, and the data therefore could not be used for calculation of the amount of starch reaching the abomasum.
