Effects of ammoniation of brome-alfalfa and alfalfa hay, stored as large round bales on preservation and feed quality

Feeding trials with growing steers and digestibility trials with sheep were conducted during each of 3 yr in a split-split plot design, to compare the effects of anhydrous ammonia (2% wt wt-1, in plastic-covered stacks of large round bales) on preservation of brome-alfalfa and alfalfa hay harvested at < 20 and at 30% moisture with respective field cured (< 20% moisture) nonammoniated hays. Even after 14 wk of storage, the ammoniated high-moisture hays were free of visible molds. Dry matter (DM) recovery varied from 93.9 to 98.7% but was not affected by either moisture content or ammoniation. Ammoniation increased (P < 0.05) acid detergent insoluble nitrogen (ADIN, % total N) in high-moisture brome-alfalfa hay to 16.8 from 9.7% in nonammoniated hay. Within each type of hay, dry matter intake and average daily gain of growing steers were not affected by treatment. Feed efficiency was reduced (P < 0.05) in animals fed ammoniated high-moisture brome-alfalfa (11.2) but was improved (P < 0.05) in those fed ammoniated high-moisture alfalfa (9.8) when compared with the respective field cured hay (10.1 and 11.4). Compared to nonammoniated hay, ammoniating high-moisture brome-alfalfa hay had no effect on digestibilities of DM and acid detergent fiber (ADF) but decreased and increased (P < 0.05) digestibility of nitrogen (N) and neutral detergent fiber (NDF), respectively. With alfalfa, ammoniation did not affect digestibilities of either low- or high-moisture hay. Rumen volatile fatty acid profiles were not influenced but rumen fluid pH was elevated in sheep fed ammoniated hays. Results indicate that anhydrous ammonia treatment effectively preserved high-moisture alfalfa without adversely affecting nutritional quality parameters.