Effects Of Fermented Green Juices On Sainfoin And Alfalfa Silage Quality And Its Mechanism

Sainfoin（Onobrychis viciifolia Scop.）and alfalfa（Medicago sativa L.）are both excellent legume forages,which play an important role in the development of ruminant husbandry in China.Silage is a widely used forage storage technology,and helps solve the problems of unbalanced distribution of forage resources and insufficient seasonal supply.However,due to the biological characteristics of leguminous forage,it is difficult to master the production process of high-quality silage.The use of microbial additives is the most widely method in silage production.Fermented Green Juices（FGJ）is a natural biological additive in the form of live bacteria which is widely used due to its economical,environmentally friendly,low cost,and simple production characteristics.Therefore,sainfoin（OS）and alfalfa（ML）were used as the research subjects in this work.A two-factorial（2 × 7）completely randomized experimental design was used to study the effect of natural fermentation（CK）,cabbage fermented green juices（BL）,oat fermented green juices（AL）,corn fermented green juices（ZL）,sweet sorghum fermented green juices（SS）,sainfoin fermented green juices（OSF）and alfalfa fermented green juices（MLF）on the fermentation quality of OS and ML silage.The effects of different fermented green juices treatments on the degradation properties of OS and ML silage that were investigated using in vitro fermentation.The silages with better quality were selected referring to the combination with the fermentation quality of silage and the results of its in vitro de-fermentation experiments.And then,high-throughput sequencing technology was used to determine the diversity and relative abundance of bacterial communities to determine the effect of different fermented green juices treatment in sainfoin and alfalfa silage.The present studies will provide a scientific basis for the targeted development of microbial additives for silage,and a theoretical support for the regulation of sainfoin and alfalfa silage fermentation in actual production.The main findings are as follows:1.After opening the silage bag,no mildew was found in all treatments.The sensory scores of OS-BL,OS-AL and ML-BL were 1 excellent,and OS-ZL was 3medium.The p H,AN/TN,LA and PA contents of the forage silage were significantly affected by fermented green juices（P < 0.05）,and the p H of OS-BL,OS-OSF and ML-AL silage groups were significantly lower than that of the other treatments,which were 4.27,4.34 and 4.27,respectively.The ratio of AN/TN in the silage groups OS-BL（12.52%）,ML-CK（12.99%）and ML-AL（12.29%）was significantly lower than in the other treatments.The LA content was significantly affected by silage material,and was higher in the ML group than in the OS group（P = 0.005）,the fermented green juices had a significant effect on the content of CP,ADF,Ash and WSC in the silage of two leguminous forages（P < 0.05）.The contents of CP in OS-BL and ML-AL groups reached 15.34%,17.28% and 17.74%,respectively.The DM,CP,Ash and WSC were higher in ML than in OS（P < 0.05）.The fermented green juices had a significant effect on the number of yeasts bacteria in silage（P < 0.05）,while it had no significant effect on the number of lactic acid bacteria（P > 0.05）.The grey correlation analysis showed that the weighted relevance and ranking of quality are CK>BL>OSF>AL>MLF>SS>ZL in OS silage group.In the ML silage group,the weighted correlation and order of silage quality were AL>BL>CK>MLF>ZL>OSF>SS.Comprehensive analysis showed that the silage quality of OS-CK,OS-BL,ML-AL and ML-BL groups were better.2.The silage materials（sainfoin and alfalfa）had a significant effect on the in vitro gas production performance of the silages.Among them,in OS silage group,the rapid degradation partial gas production（P = 0.006）,slow degradation partial gas production（P = 0.001）,potential gas production（P = 0.001）,gas production rate constant（P = 0.002）,and total gas production in vitro fermentation of OS silage were significantly higher than those of ML silage.Different silage materials also had significant effects on the silage fermentation parameters.The concentrations of acetic acid（P = 0.001）,propionic acid（P = 0.003）,acetic acid/propionic acid（P = 0.001）,isobutyric acid（P = 0.001）,butyric acid（P = 0.001）and valeric acid（P = 0.001）and TVFA were significantly higher in OS silage than ML silage（P > 0.05）,while the p H（P = 0.001）was significantly higher in ML silage than OS silage.Different fermented green juices treatments had no significant effect on the in vitro gas production characteristics and in vitro fermentation parameters of the two leguminous forage silages（P > 0.05）.3.In OS silage,the Shannon and Simpson indices of bacterial community in BL fermented green juices treatment group were significantly lower than CK and AL group.However,the two diversity indices in AL fermented green juices treatment group was significantly lower in CK and BL fermented green juices group（P < 0.001）in ML silage.The ACE（P = 0.008）,Shannon（P = 0.061）and Chao1（P = 0.011）indices of ML silage bacterial community were significantly higher than those of the OS silage.The fermented green juices,silage materials and their interaction had no significant effect on the relative abundance of bacteria at the phylum level in the two leguminous forage silages（P > 0.05）.In the OS silage group,compared with the CK,the BL fermented green juices treatment significantly increased the relative abundance of Lactobacillu（P = 0.015）and decreased the relative abundance of Weissella（P = 0.074）in silage at the genus level,while in the ML silage,the relative abundance of Lactobacillu in the silage under BL fermented green juices treatment was significantly lower than that in other treatments（P = 0.015）.The abundance of Weissella,Enterococcus and Lactococcus were significantly affected between two silage materials.In OS silage,the relative abundance of Weissella was higher than in ML silage（P = 0.055）,while the abundance of Enterococcus and Lactococcus were significantly lower than those in ML silage（P = 0.001,P =0.033）.The LEf Se clades analysis of the silage bacterial community showed that there was no significant difference in the bacterial communities of the sainfoin and alfalfa silage under natural fermentation conditions.However,the fermented green juices changed the bacterial community and significantly different species were produced and significantly changed the relationship between bacterial communities in the silage.The relative abundance of bacteria at the genus level was significantly correlated with p H,AN/TN,and organic acids（P < 0.05）.In summary,appropriate fermented green juices can significantly improve silage fermentation quality when used legumes for silage production.BL and AL fermented green juices can improve the nutrient composition and fermentation quality of OS and ML silage,respectively.BL and AL fermented green juices decreased the Shannon and Simpson indices of bacterial communities in OS and ML silage,respectively.And it can also increased the relative abundance of the dominant genus Lactobacillus which indicate that treatment with fermented green juices altered the quality of silage fermentation by changing the bacterial communities in the silage.However,the effects of the different fermented green juices were different in various silage materials.In present study,BL and AL fermented green juices had a good effect on two leguminous forages silage.