Improvement of urea treatment of wheat straw by addition of soluble carbohydrate sources in the silo.

摘要

Two completely randomized design experiments were conducted to investigate effects of addition of soluble carbohydrate sources to wheat straw ensiled with 4% urea and 100% water on the nutritional values of the straw and on the reduction of ammonia released. In experiment 1, 100% water and 4% urea, plus zero or 4% of corn, molasses, rice mill, or tapioca was mixed with wheat straw. The silo was anaerobically ensiled for 21 days at ca. 25°C, before being chemically analyzed. Crude proteins were 8.33, 7.99, 7.74 and 7.58% for molasses, corn meal, tapioca and rice meal, respectively, statistically higher than 7.02% of the control (P 0.05). Insoluble crude protein fractions were highest for molasses (6.91%) and corn (6.12%) treatments, and lowest for control (4.10%) and not significantly different from tapioca (4.55%) or rice mill (4.38%) treatments (P > 0.05). No significant differences were found in other chemical components. The greater values for crude protein of urea plus starch treated straws indicated the positive effect of soluble carbohydrate addition on CP of straw. In experiment 2, in addition to 100% of water and 4% of urea, zero or 4, 5 or 8% of corn meal or dried molasses was added to wheat straw. The mixture was anaerobically ensiled for 21 days at about 25°C. Crude protein of straw treated with corn or molasses at 4%, 6% or 8% was 8.02, 8.57, 9.06, 8.27, 9.03 or 10.07%, significantly higher than 7.03% of control straw (P 0.05). Nitrogen lost during treatment was highest for control (69%) and lowest for 8% molasses treatment (41%). Except for 4%, other levels of either corn or molasses produced a significant lower NDF content compared to control (P 0.05) (74.69 and 72.73 for 6 and 8% of corn; 71.03, 69.82 and 70.59% for 4, 6 and 8% of molasses treatments). In vitro digestibility of dry matter (IVDMD) value for control straw was 44.91%, significantly higher than 30.80% for untreated wheat straw (P 0.05). The higher digestibility and crude protein content of straw treated with starch imply that the new treatment of straw can significantly improve feed value of the treated straw.