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.