Effect of Anhydrous Ammonia Treatment on the Intake and Digestibility of Cereal Straws by Steers2

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Abstract
Three varieties each of barley, oat and wheat straw were placed in a single stack and treated with 3.5% (w/w) anhydrous ammonia. The straw bales were covered with polyethylene sheeting prior to ammoniation and held at an ambient temperature of 10 C for 42 days. Untreated and ammoniated straws were each fed to four steers together with a concentrate for 21-day periods. Straw was fed ad libitum and the concentrate at 1% of body weight for the measurement of voluntary straw consumption. Straw and concentrate were then each fed at 1% of body weight for the measurement of apparent digestibility. Ammoniation increased the average crude protein content of the straws almost threefold though improvements ranged from 50 to 276%. Data pooled across all nine straw varieties showed that ammonia treatment increased (P<.01) the apparent digestibility of dry matter, organic matter, crude fiber, crude protein and energy in the rations. Improvements in dry matter and organic matter digestibility for barley, oat and wheat straw rations were 2.2, 3.7 and 6.3 percentage units, respectively. Crude fiber digestibility was approximately 21% higher (P<.001) when treated rather than untreated straw was fed. Ammoniation resulted in significant (P<.001) increases in straw consumption, total dry matter and digestible dry matter intake. Dry matter intake responses followed the same pattern as changes in digestibility, with average increases of 6, 12 and 21% for barley, oat and wheat straws, respectively. These results show that cereal straws do not respond uniformly to treatment with anhydrous ammonia in terms of increased crude protein content, intake and digestibility. Overall responses, however, indicate that ammoniation may result in significant improvements in the nutritive value of cereal straws. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.