Study On Fermentation Characteristics And Screening Of Lactic Acid Bacteria Of Native Grassland Silage

The native grass is not only an important feed resource for ruminants but the foundation for animal husbandry.Ensiling could effectively protect the chemical compositions,improve utilization and enhance the productivity and protection of the native grass.The addition of lactic acid bacteria(LAB)could improve the fermentation quality by increasing the population of LAB when the population and ability of LAB were lower than the requirement.The composition of native grass is various and complex.The distribution of LAB and other microorganisms was diverse with the change in the composition of native grass,temporal and spatial variation,and make it difficult to get high-quality native grass silage.To date,there are still unclear on fermentation characteristics and microbial community of native grass,the correlation between the fermentation characteristics and microbial community was also confused.At the same time,no significant inoculant could improve the fermentation quality of native grass.In the present study,the meadow and typical grassland were selected as raw materials to research the alteration of chemical compositions,fermentation quality and microbial population,and combined with the microbial community.The fermentation characteristics of native grass were studied,and the correlation between fermentation and microbial community was also researched.Therefore,the characteristics and application of LAB isolated from native grass and its silages were researched.The study aimed to isolate LAB that has potential as an inoculant in the native grass based on chemical compositions,fermentation quality and microbial community.The objective of the present study was to provide technology and theory for improving fermentation quality and utilization of native grass.These results are indicated as follows.1.The dynamic of nutritional quality,fermentation quality and microbial population of meadow and typical grassland was similar.Ensiling significantly(P<0.05)decreased ADF and NDF contents,and significantly(P<0.05)increased LA contents and the ratio of LA to AA.The p H value was also significantly(P<0.05)decreased and prolonged the time for storage.The growth of yeasts,aerobic bacteria and coliform bacteria were inhibited,which is beneficial for animals.The multiple physicochemical analyses indicated that ensiling time is the dominant factor for high-quality native grass silages.2.The microbial community structure and succession of microbial richness,diversity,community composition and quantity in native grass silage were studied by Illumina Mi Seq sequencing technology.Ensiling regulated the microbial community structure of native grass silage,the richness and diversity were dropped with the increasing of fermentation.The relative abundance of Pantoea was lower than 1.00% in silages,Enterococcu,Leuconostoc,Pediococcus and Lactobacillus were the core microbiome.Interestingly,the richness and diversity of the fungal community were also dropped with the increase in fermentation.The chemical compositions and fermentation quality were reserved by decreasing the abundance of Filobasidium,Alternaria and Mycosphaeralla.Correlation analysis of the association of bacterial community with fungal community,the changes of bacterial community contributed to the difference of fungal community.3.A total of 21 LAB strains were isolated from native grass and its silages.Nine homofermentative lactic acid bacteria were isolated from native grassland and its silage according to physiological and biochemical index,growth performance and metabolic characteristics.The strain XM2(Lactobacillus plantarum)had characteristics of higher acid production,growth rate,acid tolerance and with a large range of growth temperature,The strain 925(Lactococcus garvieae)could ferment various carbon sources.Strain XM2 and 925 are the potential starter culture for native grass.4.In the present study,we used an integrated approach,combining 16 S r RNA sequencing and multiple physicochemical analyses to evaluate the effects of LAB inoculant on microbial community structure and fermentation.Lactobacillus,Pediococcus,Lactococcus,Weissella,Leuconostoc and Enterococcus were the primary genera in native grass silage,and Lactobacillus is the dominant genus for silage quality.5.The effects of isolated LAB on fermentation quality and microbial population were evaluated by the application experiments.strain 265,867 and XM2 are the potential starter culture for typical grassland,and strains XM2,162 and 880 are the potential starter culture for meadow grassland.These strains are the potential starter culture for native grass and provide a theory for inoculant on native grass silage.