The effect of method of urea-ammonia treatment on the subsequent utilization of rice straw by cross bred bull calves

Abstract

An experiment was carried out with sixty cross bred draught bull calves of 163 kg average liveweight to investigate the effect of six different methods of urea-ammonia treatment on the subsequent utilization of rice straw. Straw treated with 4% urea solution for 3, 9 and 27 days in closed pits and 3 or 9 days in open heaps was compared with untreated straw supplemented with 8·5% ground soyabean. Both 3-day treatments involved 8·5% ground soyabean added at the time of treatment as an external source of urease. Calves fed straw treated with urea and soyabean urease for 3 days in closed pits showed a daily gain of 336 ± 83 g while those on the 27-day closed, 9-day closed, 9-day open and 3-day open treatments showed daily gains of 213 ± 68 g, 307 ± 114 g, 207 ± 65 g and 308 ± 73 g, respectively. Calves on untreated straw supplemented with soyabean powder showed the lowest body weight gain of 141 ± 78 g day −1. It appears that an additional source of urease can reduce the reaction time of urea-treated straw. The 27-day closed system of treatment in cement-lined pits was not only expensive but gave weight gains similar to the 9-day open system of treatment. It is concluded that the economics of treatment and the production potential of the animal concerned should be the final factors in deciding upon the most appropriate method of treatment for farmer's use.