Aqueous ammonia treatment of wheat straw: Voluntary intake and digestibility in cattle

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Three experiments were conducted using yearling cattle weighing 235–349 kg with straw treated with aqueous ammonia (ca. 30 g NH 3 per kg straw) in plastic covered stacks. In all experiments ammoniation approximately doubled the nitrogen (N) content of straws and increased straw intake and digestibility. The chromic oxide marker technique was used to determine digestibility. In Experiment 1, daily intakes of straw dry matter (DM) and digestibility of the organic matter (OMD) of untreated and ammoniated wheat straws (cultivar ‘Bounty’) at 4.4 and 5.5 kg, and 0.43 and 0.55, respectively, were greater than those of barley straw (mixture of 3 cultivars) at 4.2 and 4.9 kg, and 0.40 and 0.50, respectively. A soya bean meal supplement had no effect on intake or digestibility of untreated straws. In Experiment 2, daily DM intake and OMD of untreated, wheat straw (‘Armada’) and the same straw treated with aqueous ammonia in a plastic covered stack or anhydrous ammonia in an “Andashstra-verter” oven were 4.3, 4.7 and 4.8 kg and 0.44, 0.50 and 0.55, respectively. In a third experiment there were significant differences in intake, but not digestibility, between straws of three wheat cultivars (‘Avalon’, ‘Flanders’ and ‘Armada’) before and after ammoniation. It is concluded that the effect of treatment of straw with aqueous ammonia by the stack method on the feeding value of straw was more variable than expected and may be related to differences between cultivars.