Screening Of Lactic Acid Bacteria From Alfalfa Silage And Study On Its Fermentation Performance

Silage is a traditional feed preservation method based on anaerobic fermentation of lactic acid bacteria,which provides a stable,reliable and predictable feed supply for ruminant production.In this study,a number of lactic acid bacteria strains were isolated from silage,the growth rate and acid production rate of isolated strains were investigated,and some strains were added to alfalfa silage to analyze the effects of different strains on the fermentation quality of alfalfa.The main results were as follows:(1)100 strains were isolated from silage by traditional culture method,and71 strains were identified as lactic acid bacteria strains by morphological characteristics,physiological and biochemical characteristics and 16 S r DNA sequence analysis.Which were Lactobacillus plantarum,Pediococcus pentosaceus,Pediococcus acidilactici and Weissella paramesenteroide,Enterococcus faecalis,Lactobacillus sp.,Fructilactobacillus sanfranciscensis and Lentilactobacillus buchneri.(2)The characteristics of the isolates were investigated,including growth rate,acid production rate,temperature tolerance,salt tolerance,acid tolerance.The isolates ZF,J3,MF1 and MF2 had higher growth rate and acid production rate and stronger tolerance,and could be used for silage fermentation.(3)After adding lactic acid bacteria strains to alfalfa silage,examine silage,nutrition composition and fermentation quality of sensory evaluation showed that the indexes of silage in the bacterial agent treatment group was better than that of the control group,group of silage inoculated Lactobacillus plantarum ZF organoleptic evaluation level for optimal treatment group,crude fiber content and neutral detergent fiber content,p H value,the contents of lactic acid and acetic acid were higher than that of control group.(4)Adding Lactobacillus plantarum ZF to alfalfa silage fermentation,the changes of nutrient composition,fermentation quality and microbial community were investigated.With the development of silage,the contents of crude protein and crude fat were increasing,while the contents of neutral detergent fiber,acid detergent fiber and soluble carbohydrate were decreasing.p H value decreased,ammonia nitrogen/total nitrogen content increased,lactic acid and acetic acid content increased;The diversity of prokaryotic and eukaryotic microorganisms decreased,and Lactobacillus firmicutes was the dominant species.Meanwhile,the fermentation quality of silage 40 d was the best,and the diversity of prokaryotic and eukaryotic microorganisms was the lowest.