不同留茬高度对构树产量、营养成分及其青贮品质和体外发酵的影响

Effects of Different Cutting Heights on Yield,Nutritional Composition,Silage Fermentation Quality and in Vitro Fermentation of Hybrid Paper Mulberry

为探究不同留茬高度对杂交构树产量、营养成分、青贮发酵品质及体外发酵的影响,本试验以生长高度为1.6 m的杂交构树为研究对象,分别设置20、35和50 cm 3个不同留茬高度进行收割(每个处理4个重复),并对其进行产量测定和营养成分分析。对不同留茬高度构树进行罐储,密度>1000 kg/m^3,室温保存45 d,开罐之后再次进行营养成分分析,并对其青贮发酵品质进行测定,最后进行体外发酵试验。结果表明:当留茬高度从20 cm增加到35 cm,构树中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)和总磷含量显著下降(P<0.05),粗蛋白质(CP)、钙(Ga)和总单宁含量显著上升(P<0.05),而构树产量、粗脂肪(EE)和粗灰分(Ash)含量无显著变化(P>0.05)。留茬高度从35 cm增加到50 cm,构树产量和NDF含量显著下降(P<0.05),EE、Ash和总单宁含量显著上升(P<0.05),而CP、ADF和总磷含量无显著变化(P>0.05)。干物质、木质素含量和缓冲能值不受留茬高度的影响,各组之间无显著差异(P>0.05)。不同留茬高度对构树青贮发酵品质影响很小,青贮pH、氨态氮(NH3 N)、乳酸、丙酸和丁酸含量在各组之间差异不显著(P>0.05)。但是留茬高度为50 cm的构树青贮中乙酸含量显著高于其他2组(P<0.05)。与鲜样相比,留茬高度为50 cm的构树青贮NDF含量显著降低(P<0.05)。不同留茬高度对构树青贮体外发酵干物质降解率(IVDMD)、产气量(GP)及发酵液NH3 N、微生物蛋白(MCP)含量没有显著影响(P>0.05)。但是相比于50 cm的留茬高度,35 cm留茬高度构树青贮能够显著增加发酵液中乙酸、丙酸、丁酸和总挥发性脂肪酸的含量(P<0.05)。综合考虑,构树最佳留茬高度为35 cm。

The aim of this study was to investigate the effects of different cutting heights on yield,nutritional composition,silage fermentation quality and in vitro fermentation of hybrid paper mulberry.In this study,pa per mulberry with a growth height of 1.6 m was harvested and three different cutting heights(20,35 and 50 cm)groups were set,respectively.After harvesting,the paper mulberry nutritional composition and yield were measured.The paper mulberry was ensiled using polyethylene bottle with a density higher than 1000 kg/m3 and preserved at room temperature for about 45 days.After ensiling,the nutritional composition,fermentation quality and in vitro fermentation tested of paper mulberry silage were conducted.The results showed that with the cutting height increased from 20 to 35 cm,the paper mulberry neutral detergent fiber(NDF),acid detergent fiber(ADF)and total phosphorus contents significantly decreased(P<0.05),crude protein(CP),calcium(Ca)and total tannin contents significantly increased(P<0.05),while the yield,e ther extract(EE)and ash contents had no significant difference(P>0.05).Cutting height increased from 35 to 50 cm,paper mulberry yield and NDF content decreased significantly(P<0.05),EE,ash and total tannin contents significantly increased(P<0.05),while the CP,ADF and total phosphorus contents had no signifi cant difference(P>0.05).The dry matter,lignin content and buffer capacity had no significant difference a mong the three different cutting heights(P>0.05).There were little effects of different cutting height on silage fermentation quality.The pH,ammonia nitrate(NH3 N),lactic acid,propionic acid and butyric acid contents had no significant difference among three groups(P>0.05).But acetic acid content of paper mulberry silage with 50 cm cutting height was significantly higher than that in other two groups(P<0.05).Compared with fresh sample,the NDF content of paper mulberry with a cutting height of 50 cm decreased significantly after ensiling(P<0.05).There was no significant difference in in vitro dry matter digestibility(IVDMD),gas pro duction(GP),NH3 N and microbial crude protein(MCP)contents among different groups(P>0.05).The acetic acid,propionic acid,butyric acid and total volatile fatty acid contents of fermentation fluid in 30 cm cut ting height group were higher than those in 50 cm group(P<0.05).Therefore,it is concluded that 35 cm is the best cutting height for paper mulberry harvesting.