Effects of Anhydrous Ammonia Treatment of Wheat Straw upon in Vitro Digestion, Performance and Intake by Beef Cattle

Abstract

Three trials were conducted to evaluate the practicality of a large scale procedure for treating wheat straw (WS) with anhydrous ammonia (NH₃) at 3.0% of the dry matter. One hundred thirty-five large round bales of WS (avg 295 kg) were covered with plastic in one stack and treated with NH₃. In trial 1, a laboratory study was conducted to evaluate the effect of location in the WS stack upon change in crude protein (CP) content, fiber digestibility and in vitro dry matter disappearance (IVDMD). Crude protein was increased from 3.6 to 11.2% by NH₃ treatment of WS. A significant location effect was observed for CP content of the wheat straw within the stack. The CP was increased 8.9 percentage units at the top of the stack and 5.9 percentage units at the bottom of the stack. Location site within the stack had no effect (P>.10) upon IVDMD of NH₃-WS. Fiber analysis before and after treatment indicated that hemicellulose was decreased 46.5% and that IVDMD of hemicellulose, neutral detergent fiber and acid detergent fiber was increased by 150, 59 and 39%, respectively, after NH₃ treatment. Treatments in trial 2 and 3 were: 1) untreated WS + soybean meal supplement and 2) NH₃-WS + corn supplement. The two treatments were calculated to be isonitrogenous and in excess of total protein and mineral requirements. In trial 2, 20 yearling heifers that were previously trained to use individual electronic feeding gates were randomly allotted to the two treatments to evaluate dry matter intake. Daily dry matter intake (DMI) of heifers receiving NH₃-WS (7.5 kg) was greater (P<.05) than that of heifers receiving untreated WS (5.8 kg). In trial 3, 90 mature pregnant beef cows were randomly allotted to the two treatments to evaluate cow performance. Cows receiving NH₃-WS lost 7.2 kg over the 90-d trial while cows receiving untreated WS lost 40.7 kg (P<.05). Visual body condition score followed the same pattern (P<.05) as weight change. The ammoniation procedure used in this study was effective and economically practical in improving the nutritive value of WS. Copyright © 1983. American Society of Animal Science . Copyright 1983 by American Society of Animal Science