In vitro Gas Production of Rice Straw Ammoniated with Different Levels of Urea

The objective of the experiment was to study in vitro gas production of rice straw ammoniated with graded levels of urea.Two Simmental cattle with average weight of 240 kg were used as the donors of rumen fluid.Five levels of urea,i.e.0,2%,4%,6%,8%(urea weight: rice straw weight) and 80% water(water weight: rice straw weight) were used for the ammoniation of rice straw.Untreated rice straw was used as the control.In vitro gas-production technique was used for the measurement of gas production of ammnoniated straw at 2,4,8,12,24,36and 48 h,respectively.The results indicated that the gas production of ammoniated rice straw increased gradually with urea level.No difference was found in 48 h gas production between 2% group and untreated straw(P0.05).The 48 h gas production of groups 4%、6% and 8% was significantly higher than the untreated straw(P0.01).The 48 h gas production of 0% group was significantly lower than those of other groups(P0.01).No differences were found in the theoretical total gas production among different groups(P0.05).The suitable amount of urea for the ammoniation of rice straw is 4%～6%.