Improvement of whole crop rice silage nutritive value and rumen degradability by molasses and urea supplementation.

摘要

Whole crop rice was harvested 120 days after planting and chopped to 2-3-cm length for silage making. The whole crop rice silage (WCRS) was supplemented with different levels of molasses and urea to study nutritive value and in situ rumen degradability. The ensiling study was randomly assigned according to a 6x5 factorial arrangement, in which the first factor was molasses (M) supplementation at M0, M1, M2, M3, M4, and M5%, and the second was urea (U) supplementation at U0, U0.5, U1.0, U1.5, and U2.0% of the crop dry mater (DM), respectively. After 45 days of ensiling, temperature, pH, chemical composition, and fermentation end products of the silages were measured. Ten U and M treatment combinations of WCRS were subsequently selected to study rumen degradability by nylon bag technique. The results showed that temperature and pH of the silages linearly increased with U supplementation level, while total volatile fatty acid (TVFA), acetic acid (C2) and propionic acid (C3) decreased. In contrast, increasing level of M supplementation decreased WCRS temperature and pH, whereas TVFA, C2, and C3 concentrations increased dramatically. Both M and U supplementation increased concentration of butyric acid (C4). Dry matter, organic matter (OM), and acid detergent fiber (ADF) contents of the silages were not influenced by either M or U supplementation. Increasing U supplementation increased crude protein (CP) content, while M level did not show any effect. Furthermore, neutral detergent fiber (NDF) content in silage was decreased by both M and U supplementation. The results of the in situ study showed that M and U supplementation increased both ruminal DM and OM degradation. The water-soluble fraction (a) was the highest in WCRS U1.5M3 and lowest in U0M0. Increasing M and U supplementation levels increased the potentially degradable fraction (b) of both DM and OM. Total rumen degradable fraction (a+b) was highest in WCRS U1.5M3, whereas OM degradability was highest in U0M3. However, effective degradation of both DM and OM were the highest in WCRS U1.5M3 and the lowest in U0M0. We conclude that supplementation of U and M increases WCRS quality and rumen degradability. Supplementation of U at 1.5 and M at 3-4% of the crop DM is recommended for lactating dairy cows and fattening beef cattle.