RATES OF DIGESTION OF SWALLOWED AND UNSWALLOWED DRIED GRASS IN THE RUMEN

Abstract

Nylon bags containing samples of dried grass and of the same grass which had been chewed and impregnated with saliva were placed in the ventral rumen sacs of two steers. The rates of digestion of the dry matter, crude fiber, crude protein, and ash were measured by removing individual bags at various time intervals up to 72 hours. The amounts of dry matter, protein, and ash digested during the first hour were much greater than the amounts digested in any subsequent 1-hour period. This was attributed to an initial rapid leaching of soluble material. The digestion of the dry matter, protein, and ash in the swallowed grass during the first hour was considerably greater than in the unswallowed grass, and differences were still present 13 hours later. The digestion of the insoluble fiber was negligible until the fourth hour after the samples were placed in the rumen. Between the fourth and the fourteenth hours the digestion of the fiber in the swallowed grass was more rapid than that in the unswallowed grass. It was concluded that the crushing and ensalivation which occurs during the eating of dried grass increases its subsequent rate of digestion in the rumen.