Study On Screening Of Lactic Acid Bacteria And The Quality Of Modulation Of Native Grasses On Meadow Steppe

In order to improve fermentation quality of native grasses in meadow steppe,change the traditional mowing mode,ahead the mowing time in late July could improve the utilization of native grass and guarantee the livestock forage supplement throughout the year,this study was prepared with native grasses in meadow steppe,the dry matter yield and chemical composition of native grass in meadow steppe were analyzed for clearing the nutrient levels of native grass in meadow steppe;the cutting time,moisture,length and density were carried out with 4 factors 3 levels orthogonal experiment,and in combination with microbial population,fermentation quality and chemical composition under different silage conditions to determine the optimal silage condition.Under the optimal silage condition,silage was made from different native grass,the microbial population,fermentation quality and chemical composition of native grasses with different species and ensiling days were studied,and revealed the mechanism of silage process of native grass in meadow steppe;in this study,the LAB strain with lowest pH,fastest acid production were isolated from different material and silages of native grass.Silages were made by LAB strains with isolated,commercial and cellulase for exploring the effect on microbial population,fermentation quality,chemical composition,aerobic stability and in vitro dry matter digestibility of native grass with different additives.This study used the orthogonal experiment design.combining with the class average clustering method,range method,single factor analysis of variance,two-factor variance analysis,studied the optimal silage condition and the microorganisms of native grass in meadow steppe,the silage quality of native grasses with different species and ensiling days,and the optimal additives of native grasses in meadow steppe,the results were as follows:(1)There were 33 species native grass in meadow steppe,the Baical needlegrass and China leymus had the highest DM yield,163.29 kg·hm-2 ? 107.23 kg·hm-2,among them there were 12 species native grass had higher NDF and ADF,they belonged to the Gramineae,Leguminosae,Compositae and Iridaceae,they were the dominant grasses in of natives grass.(2)Through the study of optimal silage conditions,the optimal silage condition of native grasses in meadow steppe were the moisture content was 60?70%,the cutting time was July 25,the cutting length was 1?3 cm and the density was 400?500 kg·hm-2,under this condition,the LAB,AB,Yeasts,LA,NH3-N,CP,ADF,NDF and WSC were at the optimal levels.(3)Among the five species.the LAB and WSC content of China leymus were significantly higher(P<0.05)than any other species,the coliform and molds content of Scabrous hideseedgrass were significantly lower(P<0.05)than any other species,During ensiling,the organic DM.CP.EE and WSC contents in each kind of silage differ significantly(P<0.05),the OM,NDF and ADF in each kind of silage did not differ significantly(P>0.05):the species and ensiling days had significantly effect on the microbial population(P<0.01),at the end of ensiling,LAB contents became the dominant.and coliform and molds were below detectable levels in all silages.During the ensiling process,the pH value and the content of NH3-N were declining,the content of DM and OM remained the same,the ensiling days had significant effect on DM,OM,CP and EE(P<0.01).but the NDF(P=0.2203)and ADF(P=0.8100)was not significant.(4)48 LAB strains were isolated from native grasses and silages,by the physiological,biochemical tests and 16S rRNA sequencing,the strains belongs to five genuses,includinglactobacillus.Weisella,Pediococcus,Leuonostoc and Enterococcus,and they belongs to twelve species,including L.plantarum,E.faecium,E.durans,E.saccharolyticus,E.faecalis,Le.mesenteroides-sbusp.-dextr,Le.pseudomesenteroides,Le.citreum,W.cibar,W.kimchii.P.pentosaceus and P.acidilactici,three strains with quicker acid production and higher growth rate were screened,they were IMAUH16(L.plantarum),IMAUH49(W.kimchii)and IMAUH52(E.durans).(5)Added individually with L1(commercial strains,L.plantarum),L2(IMAUH52,E.durans),L3(IMAUH16,L.plantarum),L4(IMAUH49,W.kimchii)and CE(cellulase),the LAB and LA of L3 were significantly higher than other groups(P<0.05),the NDF and ADF of CE significantly lower than other groups(P<0.05),the L4 delayed the raise of pH and NH3-N of secondary fermentation.The fermentation quality,chemical composition,aerobic stability and in vitro dry matter digestibility of L1+CE,L2+CE,L3+CE and L4+CE were significantly higher than any other groups(P<0.05),and the LAB,LA and WSC after exposure of L3+CE were significantly lower than any other groups(P<0.05),and the yeasts and NH3-N of L3+CE were significantly lower than any composite groups(P<0.05).