Abstract
Samples of barley straw were sprayed with solutions of urea to yield treated straws containing 450–750 g dry matter (DM) per kg straw and 35.3–105.9 g urea/kg straw DM. Two kg of each treated straw was sealed in a polythene bag and stored for 6 weeks at 18°C. After storage, samples were analysed for urea nitrogen, water-soluble and insoluble nitrogen, and their DM degradability was determined by the nylon bag technique. Ammonia was released from the hydrolysis of urea. Degree of hydrolysis was significantly affected by the concentration of DM in the straw; when urea was applied at 70.5 g/kg DM the degree of hydrolysis was 100 and 36.5% when the straw DM was 450 and 750 g kg −1, respectively. Raising the level of urea applied from 35.3 to 105.9 g kg −1 straw DM when the concentration of DM was 600 g kg −1 straw significantly increased the weight of urea hydrolysed. Urea treatment significantly increased the degradability of the straw after 48 h incubation in the rumen of steers. The degree of improvement in degradability was significantly affected by the DM content of the straw, but not by the amount of urea applied. Heat or antibiotic treatment of the straw showed that some hydrolysis occurred as a result of bacterial activity, but suggested that the contribution to hydrolytic activity from plant enzymes was minimal.
Published Version
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