The Effect of Addition Urea and Ensiling Period on The Quality and Chemical Composition of Wheat Straw Silages

An in vitro experiment is conducted to study the effect of adding urea (0, 1.5 and 3% on dry matter, DM basis) and period of ensiling (15, 30, 45 and 60 days) on the quality and chemical composition of wheat straw (WS) silages. All samples are treated with 10% of molasses. Results have shown that the addition of urea at the lower rate alters the color of silages from yellow to greenish yellow with the appearance of fermented fruit odor in samples ensiled for 60 days, but doubling urea level alters the color to dark yellow and brown as the ensiling period is proceeded with the appearance of ammonia odor. The estimated Fleig points decline due to increasing the level of urea, but the proceeding of ensiling period increases these points. pH of silages are increased (P<0.01) due to urea treatment but it decreases (P<0.01) due to proceeding of ensiling period. Regarding the compositional changes, results have shown that the addition of urea decreases (P<0.01) crude fiber (CF) and nitrogen free extract (NFE) contents, but it increases (P<0.01) crude protein (CP) content. Proceeding ensiling period decreases (P<0.01) CF and increases CP (P<0.05) and NFE (P<0.01). Generally , better results are accomplished at the lower level of urea and 60 days of ensiling.