Upgrading of straw by ammoniation

Abstract

In the period 1983–1985, three lots of wheat straw and three lots of barley straw were treated with 3% ammonia. Moreover, one lot of wheat straw and one lot of barley straw were treated with urea. The digestibility was determined with wethers or dry cows. The dry matter of straw is composed of 80% cell walls with cellulose (48–53%), hemicellulose (30–34%) and lignin (11–16%) as important fractions. The strong lignification of the cell walls prevents a complete utilization of cellulose and hemicellulose by rumen microorganisms. The digestibility of the organic matter and the net energy value per kg dry matter are consequently low and amounted to an average of 48.3 percentage units and 3.56 MJ. Treatment of straw with 3% NH 3 improved digestibility and energy value by an average of 11.2 percentage units and 0.75 MJ. Depending on the quality of the basic material, the observed effect was quite different. The resulting effect could be also influenced by the circumstances of the treatment. Treating the straw also improved the contents of crude protein (CP) and digestible crude proteins (DCP) from 3.4 to 8.5% and from 0.1 to 3.2% in the dry matter, respectively. With the exception of an increase in the CP content and a slight decrease of the wall content, the treatment of straw with urea had little or no influence on composition. Also, the improvement of the digestibility by 2–3 percentage units and the net energy content per kg dry matter by 0.048–0.19 MJ was small. The low urea dose (13 g kg −1 straw) and the insufficient moisture content of the straw for ureolysis could be considered as main causes for the rather poor results.