EFFECTIVENESS OF ANHYDROUS AMMONIA AS A PRESERVATIVE FOR HIGH-MOISTURE HAY

Abstract

Two experiments were conducted to determine the effectiveness of anhydrous ammonia as a preservative for high-moisture hays. In the first experiment, alfalfa hay, containing approximately 35% moisture was baled, stacked, sealed in polyethylene and treated with 1 and 2% (wt/wt) anhydrous ammonia. The plastic was removed at either 4 or 21 days after ammoniation and the bales were sampled following 4 mo in storage. The effects of ammoniation on heating, spoilage, chemical composition and in vitro organic matter digestibility (IVDOM) relative to untreated high- and low-moisture control stacks were determined. In the second experiment, ammonia was injected at the same rates into stacks of baled bromegrass hay containing approximately 30% moisture. The treated stacks were sealed for periods of 1 and 4 mo. In addition to the parameters measured in the first experiment, the bromegrass hays were fed to wethers to measure voluntary intake and digestibility in vivo. Injection of 2% anhydrous ammonia was completely effective in preventing heating and mold growth in the legume and grass hays during both the treatment period and following removal of the polyethylene cover. The 1% ammonia treatment reduced but did not prevent heat damage and mold growth. Ammoniation increased the crude protein content of all treated hays, the 2% application rate being more effective than 1%. Retention of the added N varied from 26.5 to 72% depending on application rate and duration of the treatment period. Applying 2% anhydrous ammonia to alfalfa hay prevented the decrease in IVDOM which occurred during storage in all other treatments and limited the increases in the proportion of NDF and ADF relative to the changes in these components which occurred in the high moisture control and 1% ammoniation treatments. Ammoniation of bromegrass hay did not affect voluntary intake (P > 0.05). The treated hays were readily consumed by the wethers and no toxic or other deleterious effects were observed. Ammoniation of bromegrass hay increased in vivo digestibility of all components measured except protein. In general, the increases in digestibility were greater following application of 2% than 1% ammonia and for the 119 vs. the 29 day treatment period. Key words: Anhydrous ammonia, preservative, hay, sheep, digestibility