What are the development prospects of microbial fermented feed in promoting animal growth, replacing

Microbial fermented feed is the use of microbial metabolism and reproduction to produce or modulate a green, safe and efficient feed. It has a good development prospect in promoting animal growth, replacing antibiotics, recycling waste and reducing human and animal competition for food. This paper summarizes the microbial fermented feed from the aspects of concept analysis, development background, production technology and optimization, research and application status at home and abroad. The mechanism of its action and the problems existing in its development were summarized, and its future development trend and prospect were analyzed in order to further expand the research and application of microbial fermented feed in animal production. 1. Microbial fermented feed microbial fermented feed refers to the decomposition or transformation of macromolecular substances and anti nutritional factors in the feed through microbial metabolism and bacterial reproduction under artificially controlled conditions to produce feed or raw materials rich in highly active probiotics and their metabolites that are more conducive to animal feeding and utilization. In the narrow sense, microbial fermented feed refers to a safe, pollution-free and drug-free high-quality feed containing active probiotics, which is processed by special processes such as drying or granulation by using some microorganisms with special functions and raw materials and excipients. Microbial fermentation technology provides the feed industry with a large number of products such as amino acids, vitamins, enzyme preparations, organic acids and live bacteria preparations. It can not only improve the nutrient absorption level of feed, degrade some toxins that may exist in feed raw materials, but also greatly reduce the use of antibiotics and other drug additives in animal production. 2. Microbial fermentation feed development background 2.1 lack of feed resources in recent years, the restriction of feed resources has gradually become the bottleneck of the development of the world feed industry and even animal husbandry production. Refined feed resources (such as corn, soybean meal, fish meal, etc.) are scarce and expensive, while cheap roughage is largely abandoned or burned because it cannot be fully utilized by animals, resulting in resource waste and environmental pollution. At present, China's Forage accounts for about 35% of the total grain output. It is expected that by 2020 and 2030, the proportion will reach 45% and 50% respectively, but the expected annual increment of grain is about 1%. The forage gap is inevitable, and the high-quality protein feed resources will be more scarce. Therefore, trying to use new feed materials to replace the increasingly scarce conventional feed materials will become the inevitable trend of feed development in the future. Among them, some by-products from grain deep processing (bran, etc.), agricultural and sideline products waste (crop straw, fruit residue, etc.) and industrial organic wastewater, waste residue, etc. will be an important research trend. The by-products of grain deep processing, the wastes of agricultural and sideline products, industrial organic wastewater and waste residue are rich in nutrients such as dietary fiber and protein. At present, the utilization of these resources in China is not sufficient, which leads to the low added value of these resources and the waste of resources. Especially for the utilization of agricultural and sideline products, there are serious problems, some are directly discarded, and some are incinerated. This will not only cause a waste of resources, but also cause damage to the environment. Therefore, using these resources for feed production research through microbial fermentation can not only realize the reuse of resources, but also alleviate the shortage of feed resources in China. 2.2 the harm of antibiotics the pathogenic bacteria in the intestinal tract of animals directly endanger the health of animals and are also the main source of food pollution. Since the 1950s, adding antibiotics to animal diets can significantly promote animal growth and the development of intensive animal husbandry. However, with the development of science and technology, the negative effects of antibiotics have been gradually discovered. It is mainly reflected in the following aspects: antibiotics not only destroy pathogenic microorganisms, but also destroy beneficial microorganisms in animals, destroy the balance of flora in animals, and will lead to more infections or greater diseases; The long-term use of antibiotics will lead to drug resistance of pathogenic microorganisms, resulting in drug resistance of pathogenic bacteria harmful to human health, and then affect human public health and safety; The residues and enrichment of antibiotics in animals will directly threaten human health and life safety through the food chain after eating livestock and poultry products. Based on the negative effects of antibiotics, Europe has banned the use of antibiotics on January 1st, 2006. China has also gradually banned the use of antibiotics. Therefore, it is more and more important to find a new type of feed that can replace antibiotics, inhibit the growth of pathogenic bacteria and promote the growth of livestock and poultry. two. 3 environmental pollution at present, there are some problems in the discharge and utilization of livestock manure in China. A large number of livestock and poultry feces are directly discharged or piled in the open air without treatment, causing soil and air pollution. In terms of use, it is often directly used as fertilizer, so that it can not be fully utilized and the added value is low. The research shows that the efficiency of animals to convert nutrients in feed into livestock products is only 20% - 35%, while 65% - 80% of the intake nutrients are discharged into the environment with feces. Livestock and poultry feces not only cause the land carrying capacity to exceed the standard, but also the heavy metals in feces seep into the ground, causing land and groundwater pollution. In addition, air pollutants harmful to human health such as hydrogen sulfide, methane and ammonia decomposed by feces are easy to form acid rain, causing a large amount of soil acidification, and aggravating soil pollution and water pollution. There is a shortage of concentrate feed resources, and the rich roughage resources have not been reasonably utilized, making the regeneration of waste resources become a research hotspot. At the same time, the abuse of feed antibiotics, unreasonable discharge of livestock and poultry feces, and the emergence of intensive and collectivized livestock and poultry farms have led to increased risks of livestock and poultry breeding diseases, rising breeding costs, environmental pollution, and increased pressure on food safety. These make healthy, environmental protection and safe breeding gradually become a consensus, and the development of microbial fermentation feed industry is one of the important ways to solve the above problems. 3. Research on microbial fermented feed abroad since the early 1960s, microbial fermented feed has been developed abroad. The raw materials initially used in the production of microbial fermentation feed are mainly some solid residues rich in cellulose (straw, straw, bagasse, etc.). With the development of science and technology, more and more raw materials are used. Probiotics used in microbial fermented feed or additives in foreign countries also mainly experienced two development stages. The first stage was from the 1950s to 1993. At this stage, there was a lack of supervision and scientific understanding of microbial strains, a lack of understanding of the production mode of their products, and a lack of evaluation of the safety and effectiveness of products. At that time, it was only recognized that probiotics could be used as growth promoters, so in the process of feed production and animal husbandry, it only blindly pursued the growth status of livestock and poultry, and did not recognize its possible adverse effects, and some adverse effects gradually began to appear. After 1993, it began to enter the second stage, during which it is required to have a comprehensive understanding of microbial strains, and began to comprehensively supervise the microbial strains used. For the strains used for the first time, it is necessary to go through strict application, approval and other steps. It is required to comprehensively evaluate the safety and effectiveness of strains, and gradually study and master the mechanism of probiotics and the mode of action with the host. With the progress of technology, the development of microbial fermented feed abroad is rapid. The raw materials used for fermentation are more and more widely, but they are mainly concentrated in the waste of industrial and agricultural production, which tends to the comprehensive utilization of resources and environmental governance. The number of probiotic strains used is also increasing. In 2009, the Federal Food and Drug Administration and the American Association of feed control officials allowed 46 microbial strains to be used as feed additives. More strains will be allowed in the future. In terms of the application of microbial fermented feed, at present, the proportion of microbial fermented feed in Europe and the United States and other countries and regions has been > 50%； Germany already has > 15% of pig farms use biological liquid feed; In the large-scale pig farms in the Netherlands and Finland, the application of biological feed can reach 60%; In Denmark, the proportion of pigs raised with biological feed reaches 80%; In France, the pig farms using fluid biological feed equipment account for about 15% of the total number of pig farms. 4. Research status of microbial fermented feed in China 4.1 development process the research of microbial fermented feed in China started late, but after continuous development, the biological feed industry has developed rapidly, and the product effect has been widely recognized by farmers. The development of microbial fermented feed in China can be summarized as the following three stages. The first stage is saccharified feed, silage, etc; In the second stage, the probiotic strains were first cultured, and then centrifuged, washed and dried to make microbial agents, which were added to the basic diet as feed additives, such as single cell protein (yeast powder); The third stage, that is, today's microbial fermented feed, mainly uses high-activity beneficial microorganisms to ferment cheap agricultural or industrial waste to produce high-quality protein feed, which can not only realize the reuse of resources, but also greatly improve the quality of products. four. 2 strains used in microbial fermented feed and application methods the primary problem in the production of microbial fermented feed is to select the appropriate strains. In 2013, the announcement of the Ministry of agriculture No. 2045 "catalogue of feed additives" stipulates that there are 35 kinds of microbial strains available in feed and feed additives. However, at present, the most commonly used strains of microbial fermented feed are yeast, lactic acid bacteria, bacillus, Streptococcus and some molds. Yeast for feed is mainly divided into tropical Candida, Candida Ruan, Saccharomyces cerevisiae, Rhodotorula, Pichia pastoris, etc. Feed yeast contains high crude protein, amino acids and vitamins, as well as a variety of digestive enzymes required by animals（ α- Amylase, protease, cellulase, hemicellulase, etc.) play an important role in the digestion and absorption of nutrients. Yeast cells can also directly combine with pathogens in the intestine and neutralize toxins in the gastrointestinal tract. At the same time, yeast has a strong yeast flavor, which has a certain effect on livestock to increase appetite and enhance digestion and absorption. Lactic acid bacteria can provide nutrients, directly promote animal growth, improve the micro ecological environment of the digestive tract, and regulate the immune system of the digestive tract. Its mechanism is that lactic acid bacteria will form dominant bacteria after entering the intestine, so as to inhibit the reproduction of bacteria, and it can produce a variety of antibacterial substances, inhibit or kill pathogenic microorganisms, so as to enhance the immune function of the body, improve the resistance of the body, and finally improve the growth performance and feeding environment of livestock and poultry. Lactic acid bacteria can also improve the quality of feed and improve the utilization of feed by poultry. Compared with traditional antibiotics and chemical additives, lactic acid bacteria have the advantages of no pollution, high efficiency and safety. Bacillus has strong amylase, protease and lipase activities. At the same time, it can also degrade cellulose, hemicellulose and lignin in plant feed, which can significantly promote the digestion and absorption of nutrients by animals, and then improve feed utilization. Bacillus can also consume a lot of oxygen, maintain the anaerobic environment of the intestinal tract, inhibit the growth of pathogenic bacteria, maintain the normal ecological balance of the intestinal tract, and enhance the body's immunity. Aerobic bacilli that have been used in production in China mainly include Bacillus cereus, Bacillus subtilis, Bacillus licheniformis and Bacillus megaterium. Streptococcus mainly includes Streptococcus faecalis and Streptococcus lactis. It can produce various antibacterial substances and hydrogen peroxide, inhibit the growth and reproduction of harmful bacteria, eliminate toxic and harmful metabolites, and regulate the intestinal flora. Other strains commonly used in microbial fermentation feed also include photosynthetic bacteria, Bacteroides, Trichoderma, etc. At present, there are many strains that can be used for microbial fermentation feed production, and they tend to be co fermented. Collaborative fermentation of two or more microorganisms reflects the synergy and functional complementarity between microorganisms. Therefore, the effect of mixed fermentation is better than that of single strain fermentation. However, when strains are compatible, it is required that the mixed strains should be few and precise, and that there should be synergy under the same preservation system to form common growth advantages, so as to ensure that each strain can play a role. From the analysis of the use of multiple strains, the combined fermentation of mold and yeast accounts for the majority. The research shows that the single and combined strains of Aspergillus niger, Trichoderma viride, Bacillus subtilis, Candida tropicalis and Saccharomyces cerevisiae are used to produce protein feed by solid-state fermentation of agricultural waste. The results show that the protein content of the mixed fermentation of Aspergillus niger and Candida tropicalis is up to about 37%. Because of its strong ability to assimilate starch and cellulose, mold can degrade it into yeast. It can use simple sugars such as monosaccharides and disaccharides, so that yeast can grow and reproduce well and achieve the effect of biotransformation protein feed. 4.3 production process and optimization of microbial fermented feed production process can adopt a variety of fermentation forms, such as solid fermentation, anaerobic fermentation, liquid surface fermentation, liquid submerged fermentation, membrane fermentation adsorbed on the surface of solid carrier and other forms of immobilized cell fermentation. However, solid-state fermentation and liquid submerged fermentation are the most widely used. In most cases, solid-state fermentation refers to a biological reaction process in which one or more microorganisms are fermented in a water-insoluble solid substrate with a certain humidity under the condition of no or almost no free water. In the fermentation process, due to the influence of many factors such as the carbon nitrogen ratio of materials, nutritional components, water content, pH and fermentation temperature, it should be determined according to different strains, different processes and different fermentation purposes on the basis of experiments. Sun Fubao and others successfully produced fermented feed by using the solid-state fermentation of corn husk mixed with Trichoderma Corning and Candida tropicalis, and its true protein content > 20%。 This method has the advantages of extensive process, simple technology, less investment, high yield and less environmental pollution, but it also has some problems, such as high labor intensity, easy to dye, process control and process parameters are difficult to achieve accurate measurement, and it is not suitable for industrial mass production. Liquid submerged fermentation is the main form of fermentation in modern fermentation industry. It mainly has two forms: continuous fermentation and batch fermentation. Different fermentation conditions need to be selected according to different strains. Similarly, nutrients, temperature, pH and time are the key factors to determine the success of fermentation. Zhao Haifeng et al. Found in the study on the production of cellobiase by Aspergillus niger liquid submerged fermentation that the main limiting factors are the supply of nutrients and temperature control, and the addition of bran 1 to the culture medium. 0% can significantly promote the formation of cellobiase. In addition, variable temperature culture of Aspergillus niger can shorten the enzyme production cycle. At the initial stage of culture, Aspergillus niger fully grew by using the nutrients in the culture medium, reducing sugar was basically consumed, and the activity of cellobiase was also low. Then the temperature decreased, and the growth of Aspergillus niger slowed down. Due to the depletion of glucose, the activity of cellobiase was greatly improved. With the extension of time, the activity of cellobiase gradually increased. This method has the advantages of short fermentation time, high efficiency, suitable for industrial production and convenient aseptic operation, but it has the disadvantages of large investment and high production cost. The microbial fermentation process is complex and is comprehensively affected by many factors, such as medium composition, temperature, pH and culture time. Therefore, in the research of optimizing fermentation process, how to effectively carry out the individual or combined optimization test of medium composition and culture conditions, so as to efficiently and systematically obtain microbial target products has attracted extensive attention of many scholars at home and abroad. Through unremitting efforts, the optimization method has developed from the simple single factor method to the statistical correlation method, such as orthogonal experimental design and uniform design. With the widespread popularity of computers and the development of database and its system software, more and more researchers began to use statistical software to simulate and optimize the experimental results. At present, many scholars use Plackett Burman experimental design scheme to quickly and effectively select several factors that have a significant impact on the experimental results from a large number of investigation factors through multi factor two-level experiments, and then use response surface analysis method to achieve the optimization purpose on the basis of box Behnken design or central composite design. This process optimization method can not only reduce the workload and improve work efficiency, but also has the advantages of visualization and high reliability. 4.4 the research and application of microbial fermented feed show that the percentage of weight gain (low temperature drying / high temperature drying) after 42 days of feeding with fermented feed in broiler feed is 9.0% and 7.5%, and the increase of broiler weight and higher feed conversion rate may be due to higher crude protein content. Clostridium butyricum, as a dietary probiotic, has the function of regulating the balance of intestinal flora in broilers, and the weight of poultry increased by 3.7% after 42 days of feeding. Probiotics can help increase the digestibility of nutrients and improve the intestinal environment. Adding different doses of mixed probiotics, the weight gain of poultry after 35 days of feeding is 4.87%, 8.28% and 8.53% respectively [31]. The average daily gain of broilers fed with 10% microbial fermented protein feed instead of the same amount of soybean meal in the basic diet of broilers at the age of 1-21 days and 1-42 days increased by 9.6% and 11.5% respectively, the feed meat ratio decreased by 10.2% and 12.1% respectively, and the number of Escherichia coli decreased by 5.26% and 12.6% respectively. It may be that through fermentation, 95% of the anti nutritional factors of protein feed are degraded, and a variety of bioactive peptides are produced, with small peptide content > During the fermentation process, microorganisms secrete a large number of protease, produce lactic acid and other substances, which are related to factors such as digestion and growth promotion. Microbial fermented feed helps to produce a variety of vitamins, regulate intestinal flora or improve immune function. Adding 20% non anti fermentation feed to the diet of growing and finishing pigs can improve their growth performance, improve the intestinal microbial balance, and improve the digestibility of nutrients. Adding 10% fermented corn straw powder to the diet of growing and finishing pigs can reduce the feed meat ratio by 8.06%, the price by 6.73%, and the weight gain cost by 14.10%. Microbial fermented feed can improve the growth performance of piglets, save feed costs, and increase the economic benefits of pig breeding. Compared with the control group, the average daily gain of piglets in the experimental group was increased by 22%, and the difference of average daily feed intake was not obvious. The feed meat ratio was relatively reduced by 38%, and the weight gain cost was reduced by 0.78 yuan per kg. Microorganisms can promote the fermentation of feed in rumen. The addition of Bacillus natto to to calf feed will not stimulate the immune system to produce allergic reactions, but can stimulate the secretion of immunoglobulin and Th1 cytokines in the serum, so it helps to activate the calf immune system, improve immunity and promote its growth. The feed conversion efficiency increased by 15.5%, the average daily gain increased by 12.9%, the weaning time was about 7.3 days in advance, and the final weight of the calf increased by 4%. The smell of microbial fermented feed is sour and sweet, and sheep only like to eat it. It has the effects of disease resistance and prevention, enhancing body immunity, promoting growth, improving survival rate, daily weight gain, improving meat quality and flavor. The basic concentrate was replaced by 50% fermented feed, the average daily gain of sheep was 19.06% higher than that of the control group, and the content of serum urea nitrogen of sheep was reduced by 33.55%. The total milk yield of the test group was 4.40% higher than that of the control group. The content of milk components, milk density and apparent digestibility of nutrients in the diet of the test group were significantly higher than that of the control group (p< 0. 05）。 It may be that only a sufficient amount of beneficial flora can well stimulate the growth of rumen microorganisms, thereby affecting the production performance and nutrient digestibility of dairy cows. Bacillus subtilis colonized in the intestinal tract of Litopenaeus vannamei can inhibit the colonization of pathogenic bacteria in the intestinal tract and reduce Vibrio parahaemolyticus in the intestinal tract; At the same time, it can induce the production of digestive enzymes and stimulate the natural digestive enzyme activity of the host, thereby improving appetite. After fermentation by Saccharomyces cerevisiae, the content of crude protein, sugars and other useful substances in soybean meal increased, and the anti nutrients decreased, which can basically meet the growth needs of young shrimp. After feeding young shrimp with fermented soybean meal instead of 50% basic diet (fish meal) for 90 days, it was found that compared with the control group, the survival rate, final weight and specific growth rate of young shrimp were not significantly different, but the cost could be reduced by about 16.51%. Compared with the control group, the weight gain rate of Grasscarp increased by 37.8% and the feed coefficient decreased by 17.2%. After the fermentation of plant protein raw materials, gossypol, glucosinolate and other anti nutritional factors are greatly reduced, and lactic acid and other substances beneficial to the growth of fish are produced. Adding 15% compound microbial fermentation feed to the tilapia diet of soybean dregs, cassava dregs and bacterial bran, the daily gain of tilapia in the experimental group increased by 22.14%, the survival rate increased by 98.07%, and the feed coefficient decreased by 15.14%. Adding compound microbial fermented feed to tilapia basic bait can effectively improve tilapia immune ability, reduce the incidence rate of tilapia Streptococcosis, promote growth, and improve feed conversion rate. Developed countries such as Europe and the United States have studied microbial fermented feed earlier, and after continuous development and improvement, both the selection of raw materials and probiotics for production and the production technology are relatively mature and widely used. Since its inception, China's microbial fermentation feed industry has also achieved rapid development, and the product effect has been widely recognized by farmers. Its applicable objects are expanding, and it has been widely used in livestock, poultry and aquatic feed. However, the research and application of microbial fermented feed in China still need to be further improved and developed. 4.5 the action mechanism of microbial fermented feed the action mechanism of microbial fermented feed is not completely clear at present, but it is generally considered to be the result of comprehensive action. Now the following points are generally recognized. 4.5.1 improve the microecological environment of animal gastrointestinal tract. Microbial fermentation feed contains lactic acid bacteria, yeast, bacillus, Streptococcus and other beneficial bacteria. After animal feeding, the beneficial bacteria that have an absolute advantage will produce organic acids (such as lactic acid and acetic acid) to reduce the pH in the digestive tract and inhibit the growth of other pathogenic microorganisms. At the same time, many lactic acid bacteria and Streptococcus can produce bacteriocins, such as lactic acid and Streptococcus peptides, which can inhibit the growth of Salmonella, Shigella, Pseudomonas aeruginosa and Escherichia coli. Under certain conditions, some lactic acid bacteria can produce a small amount of hydrogen peroxide, which can inhibit the growth of many bacteria, especially Gram-negative pathogens. In addition, some beneficial microorganisms can produce lysozyme and inhibit the growth of pathogenic bacteria. And then improve the micro ecological environment of livestock and poultry gastrointestinal tract. 4.5.2 supplement nutrients to improve feed utilization. Microbial feed can produce a variety of unsaturated fatty acids and aromatic acids after fermentation, which has a special aromatic taste and good palatability, and can significantly improve animal feed intake. Microbial feed metabolized in animals can produce a large number of enzymes such as protease, amylase, cellulase, phytase and a variety of growth promoting factors. It can also produce a certain amount of B vitamins and amino acids, as well as some other metabolites, which are absorbed and utilized by livestock and poultry as nutrients, so as to promote the growth, development and weight gain of livestock and poultry. So that animals can maximize the use of feed and improve the utilization rate of feed. 4.5.3 prevent harmful substances from producing microorganisms. The fermented feed does not contain any antibiotics and has no toxic side effects. Beneficial bacteria can reduce the concentration of ammonia, hydrogen sulfide and other toxic gases in livestock and poultry houses, and purify the livestock and poultry breeding environment. In addition, direct feeding of microecological agents, beneficial bacteria can form a dense membrane flora in the intestine, form a biological barrier, and prevent the absorption of harmful substances and waste. 4.5.4 the beneficial bacteria in the microecological agents that improve the immune function of the body are good immune activators, which can stimulate the growth of intestinal immune organs and stimulate the body to produce humoral and cellular immunity. Direct feeding of microbial fermented feed can improve the antibody level of livestock and poultry or the activity of macrophages, enhance the immune ability of the body, and eliminate the pathogenic bacteria invading the body in time, so as to improve the resistance of animals to a variety of diseases. four. 6 problems and future development trend of microbial fermented feed although microbial fermented feed has many advantages, its development will experience a gradual improvement process. Microbial fermented feed also has many shortcomings, which are reflected in the application process. At present, in the breeding environment of our country, the development of microbial fermented feed has the following problems: the stability of microbial fermented feed products is not high; The cultivation, inoculation, drying, repacking, preservation of strains in feed production and high temperature, machinery, granulation and other processes in processing may reduce the activity of strains; The research on the action mechanism of strain is not clear; The production technology of feed needs to be further improved; There is still a lack of perfect scientific evaluation system for microbial fermented feed. In view of the problems existing in the development of microbial fermented feed at present and the further promotion of the development of microbial fermented feed, it is necessary to clarify the main direction of the development of microbial fermented feed in the future. Microbial fermented feed should not be single in function. It should not only have the effect of increasing weight and promoting growth, but also have multiple effects such as preventing and controlling diseases, eliminating fecal odor, and controlling the pollution of nitrogen and phosphorus to the environment. We should develop microbial fermented feeds for different animals, different growth stages and different diseases. Make its role more targeted and the effect more remarkable. Such as microbial fermentation feed suitable for monogastric animals. The strains used are generally lactic acid bacteria, bacillus, yeast, etc., while fungal yeast is suitable for ruminants. In terms of the use of strains, in the future, it will be more inclined to design different feed products according to the different characteristics of strains. For example, lactic acid bacteria have strong acid production capacity, but are not resistant to high temperature, and are easy to compete with some trace elements and other substances. Therefore, it is not suitable to add them to feeds, especially granular materials, but can be made into water for direct drinking and feeding. Bacillus and Streptococcus faecalis have strong tolerance and can be directly added to feed, which is convenient and practical. Note cultivation and application of new strains. In addition to some physiological bacteria currently used as production strains, there are still many dominant bacterial groups that have not been developed and utilized. At present, biologists in many countries in the world are conducting basic research on feed microorganisms in order to cultivate and develop new strains better than existing strains. Make full use of the biological characteristics and metabolites of microorganisms, such as the production of amino acids, antibiotics and other physiologically active substances; Separating useful substances from microorganisms, such as using some cheap waste as substrate to produce rich and diverse microbial fermentation feed. The screening and molecular breeding of excellent strains of microbial fermented feed can apply some principles or methods of genetic engineering and cell engineering to meet the needs of microbial strains through continuous screening and transformation. Thus, the yield, quality, function, enzyme activity and benefit of microbial fermented feed are increased. Increase the application research of fermentation process, reduce the fermentation cost as much as possible, and improve the fermentation rate of fermentation products. Using new scientific and technological means to reuse the downstream products of fermentation in order to improve the market competitiveness of microbial fermented feed. Study the effective components and structures of natural plants for antibacterial and immune enhancement, and isolate, extract and industrialized them to replace antibiotics and chemical synthetic drugs in feed. The research and establishment of molecular cloning system of feed microorganisms will also be a direction of the development of microbial fermented feed in the future. 4.7 development prospect of microbial fermented feed in China 4.7.1 national policy support and guidance to promote the healthy development of biological feed industry in order to promote the development of breeding industry and feed industry, the state has formulated a series of relevant policies and put forward the overall objectives of the feed industry in the future. That is, gradually realize safe, high-quality, efficient and coordinated development, and ensure the balance between supply and demand of feed products and quality safety; Further optimize the structure of feed industry; Improve the contribution rate of science and technology to the feed industry, and significantly enhance the international competitiveness of feed enterprises; We will further improve and perfect the legal system for the production and operation of the feed industry, ensure the sustainable and healthy development of the feed industry, and gradually transform a large feed country into a powerful feed country. In order to achieve this goal, the development of microbial fermented feed will be an important direction for the development of the feed industry in the future. Among them, the 12th Five Year Plan for the development of biological industry and the 12th Five Year Plan for the development of feed industry clearly put forward that biotechnology and biological feed in the future are of great significance in ensuring feed safety and food safety, promoting the direction of healthy and sustainable development of feed industry and industrial layout model; It is the necessary condition and material basis to promote the healthy and sustainable development of animal husbandry in China; It is a long-term strategy for the development of China's feed industry in the future. 4.7.2 the demand of downstream industries is the material basis for the development of animal husbandry. The change of people's consumption structure promotes the rapid development of animal husbandry, thus driving the continuous expansion of the feed market. With the improvement of the popularity of industrial feed, the proportion of industrial feed in the breeding industry is gradually rising, which is bound to further stimulate the demand for feed. The market of feed products in China will continue to expand. Microbial fermented feed has developed rapidly in recent years. At present, microbial fermented feed has been widely used in animal husbandry industry in China. With the strengthening of people's understanding and attention to the quality of microbial fermented feed and livestock products, as well as the rapid development of biotechnology, it will further promote the development of microbial fermented feed. four point seven. 3 technological progress and transformation of traditional breeding mode with the rapid progress of scientific and technological level, farmers' breeding concept and breeding mode began to change, large-scale, standardized and professional breeding mode developed rapidly, the popularity of industrial feed increased year by year, and the output rate of land, manpower and food gradually increased, which provided a broad space for the development of China's feed industry. Especially under the deployment of the "three strategies" and "nine actions" of the Ministry of agriculture, the concept of ecological breeding has been promoted, which has laid a good foundation for building a resource-saving and eco-friendly breeding industry. The development of feed industry and standardized breeding will improve the comprehensive utilization efficiency of resources as a whole. Among them, the rapid development of biotechnology will further promote the development of microbial fermented feed. With the development of genetic engineering, microbial strains can be modified directionally. Xie Guangrong and others linked the a-amylase gene of Bacillus subtilis with the shuttle expression vector pp43c and introduced eight kinds of protease deficient Bacillus subtilis wb800 to obtain an engineering bacterium with high secretion and expression of a-amylase. The enzyme activity is as high as 960u, which has good application potential and can promote α- Industrial production of amylase. 5. Conclusion for a long time, there have been hidden dangers in China, such as more people, less food, and lack of energy, but this also shows that microbial fermented feed has great market potential in China. At the same time, with the gradual formation of China's efficient, large-scale and intensive animal husbandry production system, it also brings a huge business opportunity for the promotion of microbial fermented feed. Microbial fermented feed has also been deeply studied by Chinese scientists and vigorously promoted by the business community. In terms of bacteria, technology, equipment and processing, some methods have been studied, such as embedding, microencapsulation, and granulation technology has also made great progress, which will vigorously promote the application of fermented feed in livestock and poultry breeding< br/>