| The rapid development and transformation and upgrading of the livestock industry,leads to increasing demand for forage,and the abundant native grass resources in China are an important source of forage.Modulating native grasses into silage can improve their palatability and digestibility,and solve the shortage of green and juicy forage in pasture areas in winter.However,the attachment of native grass lactobacilli was low,which made it difficult to ferment into high-quality silage.To improve the quality of native grass silage and ensure the efficient utilization of native grass silage,this study used typical grassland forage in Xilinhot City,Inner Mongolia Autonomous Region as silage raw material with Lactobacillus plantarum(LP,1×10~6 cfu/g),Lactobacillus brucei(LB,1×10~6cfu/g),and Lactobacillus plantarum+Lactobacillus brucei(PB,1×10~6 cfu/g),and used a two-factor test Design,microbiomics combined with multivariate statistical analysis was used to investigate the changes in nutritional quality,fermentation quality,microbial population,aerobic stability,and microbial community structure during the fermentation and aerobic exposure of native grass silage.The effects of different fermentation types of lactic acid bacteria on the quality of native grass silage and the correlation between the changes in microbial community structure and the quality of native grass silage were clarified.To provide theoretical basis and technical support for improving the quality of native grass silage and ensuring the efficient utilization of native grass silage.The main findings of this thesis are as follows:(1)The addition of lactic acid bacteria significantly improved the quality of native grass silage,with the best results in LP and PB.After 60 d of silage,the p H value of LP group was significantly lower than other groups(P<0.05)and decreased to 4.2;the lactic acid content of LP and PB groups was significantly higher than other treatment groups(P<0.05),with 431.11%higher in LP than CK group and 384.76%higher in PB than CK group;PB had the lowest ammoniacal nitrogen content in all treatment groups,which could better preserve crude protein;The lactic acid bacteria added groups all preserved dry matter better,increased the number of lactic acid bacteria and decreased the number of E.coli and mold.(2)During the aerobic exposure of native grass silage,the addition of LB and PB significantly inhibited silage quality deterioration,while the addition of LP may have the opposite effect.The LB and PB groups effectively inhibited the degradation of crude protein,slowed down the increase of p H,suppressed the increase of E.coli,yeast,and mold,and significantly improved the aerobic stability of native grass silage,in which LB increased the aerobic stability by 171.69%compared with the CK group.In contrast,LP increased the ammoniacal nitrogen content and accelerated the degradation of crude protein compared with CK group,and had no significant effect on improving the aerobic stability of native grass silage,which was not conducive to the nutrient preservation during aerobic exposure of native grass silage.(2)During the aerobic exposure of native grass silage,the addition of LB and PB significantly inhibited the deterioration of silage quality,while the addition of LP had the opposite effect.the LB and PB groups effectively inhibited the degradation of crude protein and the increase of p H,E.coli,yeast and mold,and significantly improved the aerobic stability of native grass silage,in which LB increased the aerobic stability by 171.69%compared to the CK group.In contrast,LP increased the ammonia nitrogen content and accelerated the degradation of crude protein compared to CK group,and had no significant effect on improving the aerobic stability of native grass silage,which was not conducive to nutrient preservation during aerobic exposure of native grass silage.(3)The addition of different fermentation types of lactic acid bacteria significantly changed the bacterial community structure of native grass silage.Firmicutes all replaced Proteobacteria as the dominant bacterial phylum after silage.At the species level,Limosilactobacillus＿fermentum was the dominant bacterium in the CK group,Lactiplantibacillus＿plantarum in the LP group,and Lentilactobacillus＿buchneri in both the LB and PB groups;After aerobic exposure,the treatment groups remained with Firmicutes as the dominant phylum,where Proteobacteria abundance was elevated in the CK group and Bacteroidota appeared in the LP group.at the species level,the CK group was dominated by Levilactobacillus＿brevis,and Enterobacter＿cloacae.The LP group was more heterogeneous,with Lactiplantibacillus＿plantarum,Lentilactobacillus＿buchneri,and unclassified＿Muribaculaceae as the dominant species.Both LB and PB treatment groups were dominated by Lentilactobacillus＿buchneri.(4)In the silage of native grasses,Lactiplantibacillus＿plantarum and Lentilactobacillus＿buchneri were negatively correlated with p H and ammonia nitrogen,and positively correlated with crude protein,lactic acid,and acetic acid,which were the key flora for the silage quality improvement of native grasses.And Fusobacterium＿varium,Escherichia＿fergusonii,Akkermansia＿muciniphila was positively correlated with p H and ammonia nitrogen,and negatively correlated with crude protein,which were the key flora for reducing the quality of natural forage silage;during aerobic exposure,Enhydrobacter,Enterobacter＿cloacae,Moraxella＿osloensis was positively correlated with p H and ammonia nitrogen,and negatively correlated with crude protein,lactic acid,and acetic acid,which were the key flora for the decrease of quality of native grass silage during aerobic exposure. |
