Effect of Silica in Forages upon Digestibility

Abstract

Silica that is absorbed and metabolized by forage grasses has been found to be an important factor in the reduction in digestibility of cell-wall constituents. In some species, reed canary grass and possibly Coastal Bermuda grass and tall fescue, silica may rival lignin in importance. An average decline of 3.0 units of digestibility per unit of silica in the dry matter has been found. This correction has been incorporated in the Summative Equation to give: digestibility = 0.98 (100-W) − 12.9 + W (1.473 − 0.789 log L) − 3.0 (SiO2), where W is cell walls, SiO2 is silica on a dry matter basis, and L is the lignin content of acid-detergent fiber. Silica does not appear to be an important factor in the digestibility of alfalfa and perhaps other legumes.