稻草在自然风干过程中的养分变化及适宜青贮时间研究

本研究利用成熟期收获的武香粳14新鲜稻（Octavia sativa）草进行自然风干处理，研究稻草在自然风干条件下饲用品质的变化动态，并进行青贮，分析青贮发酵品质和微生物群落的动态变化，明确稻草在自然风干过程中的养分动态以及稻草适宜青贮加工的时间界限，为解决农区稻草焚烧、提高稻草饲用率提供指导。结果表明，新鲜稻草在自然风干72 h内的饲用品质呈现持续下降趋势，其中9 h之内的下降幅度平缓，24 h之后下降幅度加快，非结构性碳水化合物（NSC）从16.65%降至13.54%；随着风干时间的延长，淀粉含量呈直线下降趋势，从6.80%降至3.32%，下降幅度在50%以上；可溶性碳水化合物（WSC）含量随着风干时间的延长呈现降-升-降的趋势，风干0-3 h内呈下降趋势，3-24 h内呈上升趋势，而后又缓慢下降；干物质体外消化率（IVDMD）则呈逐渐下降趋势，从风干0 h 的44.56%下降到24 h的37.55%， 72 h后下降为34.90%。稻草经不同时长风干后的青贮发酵品质的变化趋势为风干9 h内，乳酸（LA）含量从44.87降到24.45 mgg-1，而在风干24 h后则降为12.41 mgg-1，风干48 h后降为8.74 mgg-1，风干72 h后仅为4.50 mgg-1；氨态氮/总氮（AN/TN）含量的变化对照（自然风干0 h）为44.63 mgg-1，风干3 h后则降为21.39 mgg-1，之后在风干6-9 h时又出现回升，9 h后持续下降；pH值在0-72 h内持续上升。综合饲用品质和青贮发酵品质的变化，稻草经3 h风干青贮发酵品质最好，风干24 h内青贮加工较为适宜，风干24 h后再青贮则青贮品质急剧下降。

The feeding quality dynamics of rice straw during natural wilting and the selection of suitable ensilaging time

In the present study, one japonica rice (Octavia sativa) variety, Wuxiangjing 14, was used to investigate the dynamics of the feeding quality, the silage fermentation quality and microorganisms of straw during natural wilting period, so as to determine the suitable time for rice straw ensilaging and provide instructions for the straw forage utilization. The results indicated that the feeding quality related traits of fresh rice straw showed a declined trend during the natural wilting 72 h which slowly decreased in the first 9 h and the decrease ratio accelerated after wilting 24 h. The nonstructural carbohydrates content (NSC) in rice straw decreased from 16.65% to 13.54%. With the extended of wilting period, the starch content in the rice straw continuously decreased from 6.80% to 3.32% and water soluble carbohydrates (WSC) decreased in the first 3 wilting hours, then increased from wilting 3 h to 24 h, and then decreased slowly afterwards. The fermentation quality of rice straw during natural wilting 72 h significantly changed. In vitro dry matter digestibility（IVDMD）decreased continuously, from 44.56% of wilting 0 h to 37.55% after wilting 24 h, then decreased to 34.90% after wilting 72 h. The lactic acid (LA) content of silage decreased from 44.87 to 24.45 mgg-1 in the first 9 wilting hours, decreased to 12.41 mgg-1 after wilting 24 h, 8.74 mgg-1 after wilting 48 h and 4.50 mgg-1 after 72 h. The NH3 N/total N (AN/TN) content of wilting 0 hour was 44.63 mgg-1, and then dropped to 21.39 mgg-1 after wilting 3 hour which followed by increasing between wilting 6 h and 9 h and continuously decreasing afterwards. The pH value increased during the whole wilting period. These results suggested that the fermentation quality of rice straw was the best after natural wilting 3 h which was the best ensilaging time and rice straw had good silage quality in the first 24 h.