| Silage is an important roughage source for ruminants.High-quality and safe silage is an important prerequisite for ensuring the health of livestock and improving the quality of livestock products,and is a guarantee for promoting the efficient development of animal husbandry.Lactic acid bacteria are often used as silage additives to improve the quality and safety of forage silage.Currently,lactic acid bacteria strains are often isolated from plant-derived materials such as fresh grass or silage.As an important part of the host digestive tract,animal-derived lactic acid bacteria have potential probiotic functions and are usually used directly as feed additives.However,there are few reports on the effects of animal-derived lactic acid bacteria on silage fermentation quality and in vitro rumen fermentation characteristics.Therefore,this study isolated and screened dominant lactic acid bacteria from cattle faces and added them to alfalfa silage to study their effects on the quality of alfalfa silage and in vitro rumen fermentation characteristics,and to provide a theoretical basis for development and utilization of animal-derived lactic acid bacteria as silage additives.The main findings are follows:1.Isolation,screening and identification of animal-derived dominant bacteria: 53 strains were isolated from the fresh feces of Simmental cattle.Based on growth ability and acid production rate,two dominant strains,FN-10 and FW-14,were screened.Morphological observation and Gram staining showed that the two dominant strains were Gram-positive bacilli.The homology comparison of 16 S r RNA gene sequences showed that FN-10 and FW-14 were 100% and 99.86% similar to Lactiplantibacillus plantarum,respectively.2.Taking commercial plant-derived lactic acid bacteria MTD-1 as a control,the physiological and biochemical characteristics of animal-derived lactic acid bacteria FN-10 and FW-14 were measured,such as growth ability,acid production rate,salt tolerance,carbon source utilization range,etc.The results showed that:animal-derived lactic acid bacteria FN-10 and FW-14 have faster acid production rate and stronger salt tolerance,while plant-derived lactic acid bacteria MTD-1 has stronger growth ability and acid and alkali tolerance.The p H of the fermentation broth of FN-10 and FW-14 could drop to below 4 within 24 hours and could grow normally at 6.5% Na Cl concentration,but MTD-1 grew weakly at 6.5% Na Cl concentration.MTD-1 can grow normally in the p H range of 3.5-9.0,while FN-10 and FW-14 can only grow normally in the p H range of 4.0-8.5.MTD-1,FN-10 and FW-14 can grow at 10°C,but not at 45°C.The three strains of lactic acid bacteria can utilize most of the carbon sources for fermentation,such as fructose,cellobiose and salicin.3.Animal-derived lactic acid bacteria FN-10,FW-14 and commercial lactic acid bacteria MTD-1 were added to alfalfa silage,respectively,and the control group(CK),MTD-1 treatment group,FN-10 treatment group and FW-14 treatment group were set.After 90 days of fermentation,samples were taken to detect its effects on the nutritional quality and fermentation quality of silage.The results showed that compared with the CK treatment group,the three lactic acid bacteria could significantly increase lactic acid concentration,decreased the p H of alfalfa silage(P <0.001),decreased the hydrolysis of crude protein(P < 0.05),and improved the quality of silage.Compared with CK-treated group and MTD-1-treated group,animal-derived lactic acid bacteria FN-10 and FW-14 could significantly reduce the content of ammonia nitrogen in alfalfa silage(P<0.001).Compared with the CK-treated group,the non-protein nitrogen content of the FW-14-treated group was significantly decreased(P < 0.05),and the neutral detergent fiber content of the FN-10-treated group was significantly decreased(P < 0.05).Therefore,the animal-derived lactic acid bacteria FN-10 and FW-14 can both promote the fermentation of alfalfa silage,reduce protein loss,and reduce ammonia nitrogen production.4.In order to explore the effect of lactic acid bacteria alfalfa silage on in vitro rumen fermentation characteristics,the silage of the above four treatment groups(CK treatment group,MTD-1 treatment group,FN-10 treatment group and FW-14 treatment group)was made into alfalfa grass powder.The grass powder was placed in the rumen medium and fermented for 48 hours to determine its in vitro dry matter digestibility and volatile fatty acid content,etc.The results showed that compared with the CK treatment group,the FN-10 treatment group significantly increased the acetic acid content and total volatile fatty acids content(P < 0.05),the MTD-1treatment group significantly increased the propionic acid content in the rumen culture fluid(P < 0.05).In addition,the FW-14 treatment group had the highest total gas production and in vitro dry matter digestibility at 48 hours,but there was no significant difference between the FW-14 treatment groups and other treatment groups.The lactic acid bacteria MTD-1 and FN-10 were incubated in rumen fluid in vitro for48 hours,respectively.The test results showed that both FN-10 and MTD-1 could survive in rumen fluid in vitro for 48 hours,but with the extension of incubation time,the viable counts of MTD-1 and FN-10 in the rumen fluid gradually decreased,and the viable bacterial count of FN-10 was significantly higher than that of MTD-1 in the rumen fluid at the 24 th hour(P < 0.05).In conclusion,in this study,the screening of animal-derived dominant lactic acid bacteria and the determination of their physiological and biochemical properties,and the effects of animal-derived lactic acid bacteria on alfalfa silage fermentation and in vitro rumen fermentation were carried out.The results provide a basic theory for the development and utilization of animal-derived lactic acid bacteria preparations.The data preliminarily verified that animal-derived lactic acid bacteria have the potential to be used as silage additives. |
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