DISSOLUTION OF SILICA FROM DRIED GRASS IN NYLON BAGS PLACED IN THE RUMEN OF A COW

Abstract

Samples of dried green (5.8% silica) and weathered (9.4% silica) rough fescue grass (Festuca scabrella Torr.) were placed in nylon bags and subjected to digestion in the rumen of a fistulated cow for up to 24 hr, and then analyzed for silica. The diet of the cow was either prairie hay, which saturated the rumen fluid with silica, or alfalfa hay, which did not. More silica dissolved from the samples when the cow was fed alfalfa hay than when fed prairie hay. The absolute and the proportionate amounts of silica that dissolved from weathered grass were greater than those dissolved from green grass, in the presence both of alfalfa hay and prairie hay. Silica that had dissolved in saliva squeezed from swallowed hay was about 1% of the total silica in the hay. The experimental results and microscopic observations indicate that silica in grass is composed of fractions with different tendencies to dissolve during digestion.