In Vitro Digestion, Chemical Composition, and Fermentation of Ammoniated Grass and Grass‐Legume Silage1

Abstract

AbstractPost harvest treatment of low‐quality grass hays with anhydrous ammonia (NH3) has been demonstrated to improve energy availability and crude protein concentration. Two experiments were conducted to determine what effect NH3treatment would have on the composition, fermentation, and digestibility of grass and grass‐legume silage. In the first experiment mature first‐cutting orchardgrass (Dactylis glomerataL.) herbage was harvested, ammoniated at 0, 7.5, 15, and 30 g/kg dry weight (DW), and ensiled at a moisture concentration of 703 g/kg wet weight (WW) for 8 weeks. The ensiled herbages had pH values of 4.4, 4.8, 5.8, and 5.9, respectively. Ammoniation at 7.5, 15, and 30 g/kg DW increased the concentration of total N by 5, 11, and 24 g/kg DW, respectively. Ammoniation at 30 g/kg DW increased (P<0.05) in vitro digestibility of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, and cellulose by 104, 132, 110, 132, and 128 g/kg, respectively. Ammoniation at 7.5 and 15 g/kg DW had no effect (P>0.05) on the digestibility of DM or any fiber constituent. In the second experiment, mature first‐cutting herbage composed of approximately 90% orchardgrass and 10% white clover (Trifolium repensL.) was ammoniated at 0,15, and 30 g/kg DW prior to ensiling for 10 weeks at a moisture concentration of 635 g/kg WW. The silages had pH values of 4.7,6.8, and 7.1, respectively. Ammoniation at 15 and 30 g/kg DW increased (P<0.05) the concentration of total N by 14 and 23 g/kg DW, respectively. Ammoniation at 15 and 30 g/kg DW increased (P<0.05) the extent for in vitro NDF digestion by 126 and 236 g/kg NDF. Rate constants for in vitro NDF digestion did not differ (P>0.05) among ammoniated silages but were greater (P<0.05) than those observed in the control. Rate constants averaged 0.061/h for the ammoniated silages and 0.051/h for the control.