混贮模式对高丹草青贮发酵品质及体外产气动力学特性的影响

Effects of mixed silage modes on the fermentation quality and in vitro gas dynamics of a sorghum-sudangrass hybrid(Sorghum bicolor×Sorghum sudanense)

为了解决高丹草因水分高造成青贮发酵品质不佳的问题,通过添加不同种类干草(玉米秸秆、小麦秸秆和苜蓿干草)及干草添加量(12.5,25.0,37.5和50.0kg/t)对混贮高丹草营养价值、青贮发酵品质及体外产气动力学特性进行了研究。结果表明,单独青贮高丹草的丁酸含量较高,弗氏评分等级仅为"可",添加干草混贮可显著提高青贮高丹草的发酵品质,从添加干草的种类来看,添加小麦秸秆组青贮发酵品质最高,添加苜蓿干草组营养价值最高,苜蓿干草组的体外72h干物质消失率(IVDMD)、产气速率(c)和达到最大产气量1/2时的产气速率(AGPR)均为最高,3种干草在72h累积产气量、理论最大产气量以及产气延滞时期方面差异不显著(P>0.05);从干草的添加量来看,添加25.0kg/t干草的青贮发酵品质最优,达到产气量1/2所需要时间也最长,添加50.0kg/t干草的营养价值和IVDMD最高,添加37.5kg/t干草的产气速率和AGPR最大,添加不同重量干草对混贮高丹草的72h累积产气量、理论最大产气量以及产气延滞时期无显著影响(P>0.05)。综合考虑青贮发酵品质和饲料营养价值,得出最佳的混贮模式为在高丹草中添加37.5kg/t小麦秸秆,添加50.0kg/t苜蓿干草混贮高丹草的体外干物质消失率最高,添加37.5kg/t苜蓿干草组产气速率最快,添加50.0kg/t小麦秸秆组的72h累积产气量和理论最大产气量最高。

The fermentation quality of sorghum-sudangrass hybrids（Sorghum bicolor×Sorghum sudanense）is poor because of their high moisture contents.In this study,we analyzed the effects of different storage modes on the fermentation quality of a sorghum-sudangrass hybrid.A sorghum-sudangrass hybrid was mixed different types of hay（corn stalk,wheat straw,and alfalfa hay）at different proportions（12.5,25.0,37.5and 50.0kg/t）.Then,the nutritive value,fermentation quality,72 hdry matter digestibility,and gas dynamics were measured using an in vitro system that simulated rumen fermentation.The results showed that the silage produced from the sorghum-sudangrass hybrid had a high butyric acid content,and a poor Flieg evaluation ranking.The addition of all types of hay significantly improved the fermentation quality of stored silage.The addition of wheat straw resulted in the best fermentation quality,while the addition of alfalfa hay resulted in the best nutritive value.The addition of alfalfa hay resulted in the highest values for IVDMD（in vitro dry matter digestibility）,c（gas production speed）,and AGPR（speed when gas production was one-half of the maximum）.There was no significant difference in GP72h（accumulated gas production in 72h）,A（ideal maximum gas production）,and lag（lag time of gas production）among silages produced with the three types of hay.In terms of the amount of hay added,the addition of 25.0kg/t resulted in the best fermentation quality and the highest half-time content,and the addition of 50.0kg/t resulted in the best nutritive value and the highest IVDMD.The addition of 37.5kg/t hay resulted in the highest c and AGPR values.The amount of hay added did not significantly affect GP72 h,A,or lag.Considering the nutritive value and fermentation quality,the best mixed silage was produced by adding 37.5kg/t wheat straw.The addition of 50.0kg/t alfalfa hay gave the highest IVDMD content,the addition of 37.5kg/t alfalfa hay gave the highest gas production rate,and the addition of 50.0kg/t wheat straw resulted in the highest GP72 hand A.