AMMONIA OR SULPHUR DIOXIDE TREATMENT OF HIGH-MOISTURE BARLEY ON IN SITU RUMEN DEGRADABILITY AND IN SITU WHOLE-TRACT DIGESTIBILITY

High-moisture barley (HMB) was ensiled in polyethylene silage bags. Treatments applied to 30% moisture HMB as a percentage of dry matter (DM) were: none, 1% ammonia, 2% ammonia, and 1.5% sulphur dioxide. A fifth treatment was the addition of 1.5% sulphur dioxide to 20% moisture HMB. Barley samples were ruminally incubated to estimate degradability of DM and nitrogen (N). Ruminally incubated bags were also introduced to the duodenal cannulae and collected in feces to estimate true whole-tract digestion. Sulphur dioxide treatment, or moisture content, had no influence on ruminal degradability, with the exception of increased degradation rate of potentially degradable N for 20 vs 30% HMB, or whole-tract true digestion. Ammoniation resulted in net reduction in rate of ruminal DM release due to shift of soluble DM to the potentially degradable fraction, and decrease in the potentially degradable fraction degradation rate. Ammoniation increased barley N content up to 44% with no change in rate of ruminal N release. Whole-tract true DM digestion was higher for ammoniated barley but N digestion was not influenced. Sulphur dioxide appears to offer no advantages beyond grain preservation, whereas ammoniation offers potential by reducting rate of ruminal DM release, and providing a source of slow release nonprotein N, without affecting post-ruminal digestibility. Key words: High-moisture barley, ammonia, sulphur dioxide