Nitrogen Fractions of Alfalfa Silage from Oxygen-Limiting and Conventional Upright Silos

Abstract

Alfalfa silage from oxygen-limiting (39 samples) and conventional upright silos (43 samples) sent to the Virginia Tech Forage Testing Laboratory from September 1984 to April 1985 were randomly selected and analyzed for dry matter, fiber, and nitrogen fractions. Crude protein and neutral and acid detergent fiber were not different for oxygen-limiting and conventional upright silo samples. Dry matter, and buffer-insoluble nitrogen, neutral and acid detergent insoluble nitrogen, and nitrogen insoluble in neutral but soluble in acid detergent, expressed as a percent of total nitrogen, were greater in silage from oxygen-limiting than from conventional upright silos. A greater percentage of samples from oxygen limiting silos had acid detergent insoluble nitrogen content greater than 15% compared with samples from conventional upright silos (35.9 vs. 14.0%).Regression equations were formulated for dry matter versus acid detergent insoluble nitrogen. Dry matter, dry matter squared, and dry matter cubed accounted for only 34 and 35% of the variation in acid detergent insoluble nitrogen in conventional upright and oxygen limiting silos, respectively. Other factors must be considered to predict accurately acid detergent insoluble nitrogen.