Hay Preservation and Quality Improvement by Anhydrous Ammonia Treatment

A study was conducted to determine the effectiveness of anhydrous ammonia (NH₃) as a preservative to prevent microbial activity and consequent dry matter and digestibility losses in hay that is intentionally or unintentionally stored at moisture levels above 20%. An effective hay preservative would shorten required drying time, thus reducing mechanical losses and risk of weather damages. Alfalfa (Medicago sativa L.), tall rescue (Festuca arundinacea L.), and ladino clover (Trifolium repens L.)-tall rescue hays were baled at moisture contents ranging from 16 to 33%. Immediately after baling, gaseous NH₃ was applied at 1.0% of the weight of the hay. Temperatures were recorded for three weeks following treatment. Dry matter and digestibility losses were measured in samples taken at baling and after 2 or 3 months in storage. All of the untreated hays with initial moisture contents above 32% became moldy, heated to 55 C or above, and suffered significant losses in dry matter, in vitro dry matter disappearance (IVDMD), and in vitro cell wall disappearance (IVCWD) during storage. Ammonium N,acid detergent fiber (ADF), neutral detergent fiber (NDF), and ADF-N percentages increased significantly. Total N percentage of alfalfa hay increased significantly during storage. NH₃ treatment reduced molding, heating, and dry matter loss in stored hay. Significant increases in total N, ammonium-N, and IVCWD occurred following NH~ treatment. IVDMD decreased during storage but remained higher than in untreated hay. Animals readily consumed the ammoniated hay. NH₃ has the potential to preserve hay that is too wet to store without a preservative. In addition, ammoniation may improve hay quality by increasing total N content and cell wall digestibility. Ammoniation of highly lignifled, low N materials such as corn stalks, corn cobs, or straw might significantly improve nutritional quality of these materials.