Effects Of Different Carbon Sources On Quality And Microbial Community Structure Of Caragana Korshinskii Silage

Caragana korshinskii is a legume non grain feed with high content of crude protein,vitamins and amino acids.However,the nutrient content of Caragana korshinskii Kom.Varies greatly in different growth stages.Moreover,Caragana korshinskii has high content of crude fiber and tannin,which limits its development and utilization.Silage can alleviate this problem.However,because of the low content of soluble compounds,direct silage is not easy to succeed.In this experiment.Caragana korshinskii was silaged with glucose,sucrose and starch as carbon source additives in bud stage and full bloom stage.By comparing the changes of fermentation quality,nutritional quality and microbial community structure of Caragana korshinskii silage,the best growth period,the best type and amount of carbon source additives were selected.(1)The results of Experiment 1 showed that glucose,sucrose and starch could improve the fermentation quality of Caragana korshinskii silage,significantly reduce the pH value(P<0.05),increase the lactic acid content,and the sensory evaluation was above good.The pH value of Caragana korshinskii silage was significantly lower than that of the control group(P<0.05),and the acetic acid content of 1.5%and 2.0%carbon sources was significantly lower than that of the control group(P<0.05);The addition of 1.5%and 2.0%carbon source could reduce the content of ammonia nitrogen and propionic acid,but the effect was not significant(P>0.05).In addition to 2.0%glucose and sucrose addition,the pH value of Caragana korshinskii silage was significantly decreased in Caragana korshinskii glucose and sucrose addition groups(P<0.05),and only 0.5%starch addition significantly decreased the pH value of Caragana korshinskii silage(P<0.05);All carbon sources increased the ammonia nitrogen content of Caragana korshinskii silage.The ammonia nitrogen content of glucose and starch was significantly increased(P<0.05),but the ammonia nitrogen content of sucrose was not significantly increased(P>0.05);The results showed that three kinds of carbon sources had effects on the organic acid content of Caragana korshinskii silage in full bloom stage:only 1.5%sucrose and 1.5%starch could significantly increase the lactic acid content of Caragana korshinskii silage(P<0.05).Compared with the propionic acid content of the control group,the acetic acid content of Caragana korshinskii silage with each addition of sucrose except 0.5%sucrose was significantly lower than that of the control group(P<0.05),The content of acetic acid in 1.0%starch group was significantly lower than that in the control group(P<0.05),and the effect of three carbon sources on propionic acid content of Caragana korshinskii silage was not significant(P>0.05).According to the laboratory and sensory evaluation indexes of fermentation quality,the best addition amount of three carbon sources was 1.5%.(2)The results of Experiment 2 showed that the content of crude protein and soluble sugar in Caragana korshinskii was higher in full bloom stage,and its nutritional quality was better than that in bud stage.The interaction between growth period and carbon source treatment affected the fermentation quality of Caragana korshinskii(P<0.05).The contents of dry matter,crude fat and soluble sugar were affected by the interaction between growth period and treatment(P<0.05).The contents of crude protein,crude fat,neutral detergent fiber,acid detergent fiber and crude ash were not affected by the interaction between growth period and treatment(P>0.05).The pH value of each treatment was significantly lower than that of the control group,and the lactic acid content of each treatment was higher than that of the control group(P>0.05).The number of lactic acid bacteria and yeast were affected by the interaction of growth period and treatment(P<0.05),and also by the single effect of growth period and treatment(P<0.05).There was no interaction between growth period and treatment on microbial diversity(P>0.05),but there was interaction on microbial abundance(P<0.05).The dominant bacteria in the control group were Firmicutes,Proteobacteria and Actinobacteria.The abundance of Firmicutes decreased and the abundance of Proteobacteria and Actinobacteria increased after adding carbohydrate;At the genus level,the dominant bacteria in the control group were Lactobacillus and Pediococcus.The carbon source additives reduced the abundance of Lactobacillus,and increased the abundance of Weissella,Leuconostoc,Sphingomonas,Ralstonia and Enterobacter.Ascomycota and Basidiomycota were the dominant fungi in all treatments;At the genus level,the core biota were Didymella,Penicillium,Cutaneotrichosporon,Alternaria,filobasidium and unclassified fungi.In conclusion,Caragana korshinskii silage with 1.5%sucrose during gestational bud stage had the best fermentation quality and nutritional quality.