Digestibility of Forages In Vitro as Affected by Content of “Silica”2

Abstract

Digestibility of organic matter was assayed in 76 samples of forage representing eight species of plants samples at various stages of growth and maturity, through fermentation by rumen microorganisms cultured in vitro. Digestibility of organic matter was related to forage content of chemical constituents (nitrogen, ash, ether extract, cell-wall constituents, acid-detergent fiber, acid-detergent lignin and crude silica) in multiple linear regression equations. Stepwise regression analysis showed that digestibility of organic matter in the samples is predicted most accurately by an equation which considers only cell-wall constituents (CWC), acid-detergent lignin (ADL), silica and ether extract (EE): IVOMD=155.3−1.09 (%CWC)−2.74 (%ADL)−0.98 (% silica)−1.89 (%EE). The relationships indicate that silica decreases the digestibility of organic matter by approximately 1% for each percentage increase in the silica content of the forage.