Research progress and application of microbial fermented feed

With the rapid development of animal husbandry and the increasing market demand, the price of feed raw materials continues to rise, and the cost of feed for breeding enterprises is increasing. Therefore, the research and development and production of new low-cost feed raw materials have attracted attention. Silage has been widely used in animal production, greatly reducing production costs, but there are still many problems, such as: more nutritional loss, improper storage and easy to mold. Microbial-induced TMR (total mixed ration, TMR) fermentation has been widely used to improve feed quality. TMR silage stabilizes rumen function, avoids self-selection by animals, and may introduce undesirable by-products into the feed if its odor and flavor are altered by fermentation during silage. Lactic acid bacteria improve the fermentation process of silage, so that silage has better nutritional value, and are commonly used additives in silage. On the other hand, Bacillus subtilis are also used as silage additives because of their ability to produce cellulolytic enzymes and antifungal compounds. Among them, Bacillus subtilis as a feed inoculant can improve the aerobic stability of silage and produce enzymes such as amylase and ferulic acid esterase. Studies have shown that inoculation of Bacillus subtilis alone or in combination with lactic acid bacteria can increase the concentration of lactic acid bacteria, reduce the number of mold and yeast, improve the aerobic stability and nutritional value of corn silage, and increase the number of beneficial intestinal flora and nutrient digestibility. In addition, the co-culture of lactic acid bacteria and Bacillus subtilis can improve the quality of TMR.

Microbial fermented feed is popular because of its high value and low price in animal production. There are many types of raw materials used in microbial fermented feed, such as corn, soybean meal, cottonseed meal, rapeseed meal, apple pomace, potato pomace, and crop straw. Due to the high content of anti-nutritional factors in these feeds, they are difficult to be directly digested and absorbed by animals. As a result, the utilization rate of the feed is low. The use of microbial fermentation technology can effectively remove the anti-nutritional factors in the feed, improve the utilization rate of the feed, and the fermented feed has a stronger flavor and better palatability, so it can be better used by animals. Lactic acid bacteria, bacillus and yeast are the most common and most used microorganisms in fermented feed, and these microorganisms can effectively inhibit the growth of endogenous pathogens.

The beneficial effects of probiotics on animals are also affected by many factors, such as the colonization ability and dosage ratio of compound probiotic preparations. Therefore, it is necessary to study bacterial colonization and dose effects of probiotics by evaluating the health status of fermented feeds on animal organisms. In general, the strains will produce a series of metabolites such as organic acids, special enzymes and bacteria during the fermentation process, which can stimulate the immune system, digestive enzyme activity and intestinal microbiota, thereby improving the growth performance of animals. In addition, due to the large number of active microorganisms in the gut, which constitutes a complex ecosystem, it is crucial to evaluate the effect of feed on the gut microbiota of animals.

The definition of microbial fermented feed and its production process types

1.1 Definition of microbial fermented feed

Microbial fermented feed is to decompose plant-based agricultural and sideline products and other raw materials into some macromolecular substances such as polysaccharides, proteins and fats through the fermentation of microorganisms under the condition of human control, and generate small molecular substances such as organic acids and soluble small peptides. , to form a biological feed with rich nutrition and good palatability.

1.2 Types of production process

1.2.1 Classification by fermentation process

According to the fermentation process, fermentation is divided into: solid state fermentation and liquid state fermentation. Solid-state fermentation refers to fermentation in which there is no free water that can flow in the growth medium of microorganisms. Solid-state fermentation has a wide range of sources of fermentation substances, and has the characteristics of high concentration of fermentation end products, easy storage, and less wastewater generated during the fermentation process. Liquid fermentation refers to the process of artificially dissolving all nutrients such as sugar, nitrogen salts and inorganic salts required for the growth of strains in water as a medium in a biochemical reactor, inoculating after sterilization, and carrying out mass reproduction of bacteria . Liquid fermentation has the characteristics of wide source of raw materials, rapid bacterial growth and short production cycle.

1.2.2 Classification according to the type of bacteria used

According to the types of bacteria used in fermentation, it can be divided into single-bacteria fermentation and mixed-bacteria fermentation: the bacteria used in single-bacteria fermentation mainly include Lactobacillus, Bacillus subtilis, and yeast, and only one of them is selected for fermentation; mixed-bacteria fermentation mainly uses Aspergillus niger, wood Mold, Lactobacillus, Bacillus, yeast, etc. are mixed according to the proportion, and used for the fermentation of rapeseed meal, cotton meal, soybean straw, tea dregs, corn flakes and other miscellaneous meal or by-products of agricultural products.

1.2.3 According to the demand for oxygen

According to the needs of microorganisms for oxygen, the fermented feed process can be divided into three types: aerobic fermentation, anaerobic fermentation and two-stage fermentation. Among these three fermentation methods, aerobic fermentation is the most practical in the actual application process. This method is widely used in biological fermentation in my country. It is characterized by short fermentation cycle and high material conversion rate. Anaerobic fermentation is characterized by low fermentation respiratory loss and mellow aroma. In most cases, two-stage fermentation can be carried out, with aerobic fermentation first and then anaerobic fermentation.

2. The mechanism of action of microbial fermented feed

2.1 Creating a chemical barrier

Lactic acid bacteria account for a large proportion of the probiotics added in the feed, and can produce organic acids such as lactic acid, acetic acid, propionic acid, butyric acid, etc. The growth of pathogenic microorganisms will be inhibited in an acidic environment, especially Salmonella and Escherichia coli The growth and reproduction function of the animal is greatly weakened, thereby maintaining the balance of the intestinal microbial flora of the animal and improving the health level of the animal body.

2.2 Generation of biological barriers

Beneficial microorganisms added to the feed will inhibit the colonization of harmful microorganisms on the intestinal mucosa through competitive effects. For example, Lactobacillus acidophilus first attaches to the intestinal tract of pigs, which reduces the binding sites of E. coli and intestinal epithelium, thereby Establish a dominant flora in the gut.

2.3 Creating a nutrient barrier

The principle of microbial fermented feed is to degrade macromolecular polysaccharides and proteins into small molecular organic acids, small peptides, vitamins and other nutrients, which are easier to be digested and absorbed by objects.

3. Effect of microbial fermented feed on feed quality

3.1 Effect of microbial fermented feed on feed form, color and smell
Li Shaozhang et al. used plant lactic acid bacteria to ferment the feed, and found that the liquid-to-solid fermentation is the most ideal. The feed form gradually becomes loose with the extension of fermentation time; Afterwards, it gradually becomes gray-yellow; the smell changes from sour to sweet and finally mellow with the increase of fermentation time. Wu Jindong et al. used lactic acid bacteria to ferment the vetch and found that the feed color of the control group was yellowish brown, and the color of the feed added with lactic acid bacteria increased with the inoculation amount, and the color of the feed changed from yellowish brown to yellow and then to yellow green; The musty smell gradually appeared. With the increase of the inoculation amount of lactic acid bacteria, the smell of the feed added with lactic acid bacteria changed from a slight sour taste to aroma and sour wine. Feed, the feed is soft and loose.

3.2 Effects of microbial fermented feed on feed pH and organic acids

After fermenting cassava dregs with complex Bacillus butyricum, Wei Limin found that the pH and propionic acid content decreased significantly, the content of lactic acid and acetic acid increased significantly, and the content of butyric acid increased, but the difference was not significant, and butyric acid increased with the addition of bacterial solution volume increased with a slight decrease. Liu Quanwei et al. used compound enzyme preparations to ferment corn stalk silage, and found that the pH of the fermented product was significantly lower than that of the unfermented product, the lactic acid, acetic acid, and propionic acid increased to varying degrees, and the butyric acid content showed a downward trend.

3.3 Effects of microbial fermented feed on conventional nutritional components of feed

Cheng Fang et al. used Aspergillus niger and Saccharomyces cerevisiae to ferment potato dregs and found that the crude protein (crude protein, CP) content, protease activity, and cellulase activity of potato dregs were significantly increased (P<0.05), and the crude fiber (crude fiber, CF) content decreased significantly (P<0.05). Wei Limin et al found that adding Bacillus butyricum complex to cassava residues significantly increased the content of CP and crude fat (ether extract, EE) (P<0.05), dry matter (dry matter, DM), neutral washing The content of neutral detergent fiber (NDF), acid detergent fiber (ADF) and calcium decreased significantly (P<0.05). Meng Difang et al. used lactic acid bacteria to ferment the chaff of Pleurotus ostreatus and found that the ammoniacal nitrogen, soluble carbohydrates, NDF, and ADF in the fermentation product were not significant compared with the control group, which may be due to the increase of fermentation time. The growth of lactic acid bacteria consumes too much substrate material, which leads to the slow growth of beneficial bacteria and weakens the competition of harmful bacteria, which makes the growth of harmful bacteria faster and affects the fermentation quality. Lu Yongxiang and others fermented corn with Lactobacillus plantarum. The results showed that the ammonia nitrogen content in the fermentation product increased significantly (P<0.05). The reason for the difference from the above results may be that Lactobacillus plantarum is different from the lactic acid bacteria strains selected by Meng Difang et al., and consumes less fermentation substrate. less, thereby ensuring the normal growth and metabolism of beneficial bacteria, and the fermentation effect is good. Wu Penghao et al. added compound lactic acid bacteria preparations to the whole corn plant, and the results showed that compared with the control group (without adding bacterial agents), the starch content increased significantly (P<0.05), the aerobic stability was better than that of the control group, and the storage time was longer. long.

4. Application of microbial fermented feed in animal production

4.1 Application of microbial fermented feed in pig production
Lin et al. found that 6% fermented corncob feed significantly increased the daily intake (DI) and daily gain (ADG) of pigs (P<0.05). Slaughter performance, meat quality and other indicators have been significantly improved. In addition, beneficial bacteria such as lactic acid bacteria in the intestines of finishing pigs increased significantly, and pathogenic bacteria such as E. coli in the intestines and feces decreased significantly (P<0.05). Intestinal crypt depth and ileal mucosal immunity of finishing pigs were also significantly improved (P<0.05). The content of cytokines and gene expressions of sIgA (secretory IgA), IL-8 (interleukin 8), and TNF-α (tumor necrosis factor α) were significantly increased (P<0.05). Research by Xiong Ying et al. showed that when fermented soybean meal was added to the basal diet of nursery pigs, the ADG of the pigs was significantly increased, the feed-to-weight ratio and diarrhea rate were significantly reduced (P<0.05), and the serum immunoglobulin M (immunoglobulin M, IgM ), the content of immunoglobulin A (immunoglobulin A, IgA) was significantly increased (P<0.05), and the production performance and immunity of nursery pigs were improved. Chen Yulong et al. found that after feeding fermented soybean meal, the diarrhea rate of nursery pigs was negatively correlated with the addition ratio of fermented soybean meal, blood urea nitrogen (BUN) showed a downward trend, serum albumin (ALB), globulin The content of globulin (GLB) was positively correlated with the proportion of fermented soybean meal, and the difference was not significant. The activity of alanine aminotransferase (ALT) decreased significantly after adding 15% fermented soybean meal (P<0.05). Xin Xiaozhao et al found that after feeding fermented soybean meal, the feed intake of lactating sows, the weight of weaned piglets, and the survival rate were significantly increased (P<0.05), the interval between weaning and estrus was shortened, and the diarrhea rate of piglets during lactation was reduced. The digestion and absorption of CP, EE, calcium, phosphorus and other nutrients by the sow body; the content of milk protein, lactose, and milk fat increased, but the difference was not significant (P>0.05). (aspartate aminotransferase, AST) levels were significantly reduced (P <0.05). Choi et al. found that feeding weaned piglets with fermented kefir improved the performance of piglets, decreased the number of E. coli in feces, decreased IL-6 pro-inflammatory cytokines, increased IgM, and increased the body's immunity.

4.2 Application of microbial fermented feed in chicken production

Abuduru Suli Erken et al. found that in the late growth period, feeding soybean meal fermented by Lactobacillus acidophilus significantly reduced the feed-to-weight ratio and abdominal fat rate of broilers (P<0.05), and the whole eviscerated rate and leg muscle rate decreased significantly. Significantly improved (P<0.05). Chen Ting and others found that: adding compound probiotic fermented feed, Xuefeng black-bone chicken breast muscle rate and breast muscle brightness increased significantly (P<0.05), and breast muscle pH, cooking loss, and drip loss decreased significantly (P<0.05). Gungor et al found that feeding raw pomegranate pomace and fermented pomegranate pomace did not change glutathione peroxidase, superoxide dismutase (superoxide dismutase, SOD) and catalase (CAT ) level, but it will reduce malondialdehyde (MDA) in breast milk, high addition of raw pomegranate pomace and high or low addition of fermented pomegranate pomace can significantly reduce cecal Clostridium perfringens (P<0.05), low The crypt depth of added amount raw pomegranate pomace was higher than that of control group and high added amount group. Huāng et al. found that adding phytase-fermented wheat bran can increase the weight, thickness and strength of the eggshell, and the SOD and CAT in the serum were significantly increased (P<0.05). Phosphorus content decreased significantly (P<0.05).

4.3 Application of microbial fermented feed in sheep production

Yuxia et al. found that after feeding fermented corn stalks, the growth performance of mutton sheep was slightly improved (P>0.05), the heart weight, rumen ammonia nitrogen, and propionic acid content were significantly increased, and the ratio of acetic acid/propionic acid was significantly decreased (P <0.05). Qiu Yulang and others found that after feeding straw and corn steep liquor mixed microbial fermented feed, the ADG of mutton sheep was significantly increased, the feed-to-weight ratio was significantly reduced, and blood biochemical indicators such as total protein (TP), ALB, and BUN in blood were significantly increased. Wang Xiaoping’s research found that adding a compound bacterial agent of lactic acid bacteria and yeast to silage corn significantly increased the average daily feed intake of Tan sheep (P<0.01), decreased ADG, final weight gain, and decreased feed-to-weight ratio. The differences were not significant (P>0.05), but the trend was the same as above. Ouyang et al.’s research on growing lambs showed that adding a mixed additive of Lactobacillus plantarum, Trichoderma genus Trichoderma and wheat bran to silage straw can significantly increase the microbial protein (MCP) in the rumen fluid, and the total Volatile fatty acids (TVFA), acetic, butyric, and pentanoic Acid concentration (P<0.05). In addition, straw silage with Lactobacillus plantarum, clover and wheat bran can improve the lamb's overall growth performance, rumen fermentation capacity.

4.4 Application of microbial fermented feed in cattle production

Yu Miao and others found that after adding lactic acid bacteria and yeast to the feed, the contents of TP, ALB, IgA, IgG and IgM in the serum of beef cattle were significantly increased (P<0.05), while the MDA content, AST and ALT activities in the serum were significantly reduced , the total antioxidant capacity and the activity of total SOD were significantly enhanced (P<0.01). Suryanto et al. found that the production performance of meat-to-bone ratio, rib eye muscle area and carcass rate were significantly increased (P<0.05), and the meat quality was also significantly improved after feeding the diet fermented with cocoa bean shells. Studies by Wu Xiaoyan and others have shown that by fermenting food industry by-products with probiotics such as lactic acid bacteria, Bacillus subtilis, and yeast, the milk production of dairy cows in the whole period is significantly increased, and the milk density, lactose, milk protein, and milk fat content are also significantly increased. (P<0.05). Vailati et al. found that yeast fermentation products can reduce rectal temperature, somatic cell score and infection season temperature when adding yeast fermentation products to the challenge of mastitis in dairy cows. It was also found that yeast ferment supplementation upregulated mammary gland genes associated with immune cell antimicrobial function, epithelial tissue protection, and anti-inflammatory activity. Up-regulation of TNF-α and heat shock protein (HSP) responses in response to mastitis in dairy cows with yeast fermentation products. Other detoxification and cytoprotective functional pathways, as well as tight junction pathways, were also upregulated in yeast ferment-fed cows. Wanapat et al.’s research on beef cattle found that: feeding mulberry silage to beef cattle, TVFA and individual volatile fatty acids (volatile fatty acid, VFA) in the rumen were significantly increased (P<0.01); nitrogen use efficiency and urinary purine derivatives content increased significantly (P<0.01). Jin Hongyan et al. found that: probiotics can increase the content of acetic acid and propionic acid in the rumen of perinatal yaks, but reduce the content of butyric acid, and the difference is not significant (P>0.05). We speculate that the reason may be that the perinatal period provides energy preparation for the lactation period, and acetic acid, propionic acid, etc. provide energy for the body through the gluconeogenesis pathway, and after production and consumption, the effect is not so obvious. Neves et al. found in steers that the increase in ADG was greater in the probiotic group. There was no significant difference in feed intake among the groups, and the area of the longissimus dorsi muscle and the thickness of back fat increased. Probiotics improved performance, contributed to increased fiber digestibility, and improved carcass metrics.

4.5 Application of microbial fermented feed in other animal production

Wu Lingli et al. found that adding fermented apple pomace to the diet of rex rabbits increased nutrient digestibility and ADG (P<0.01), and significantly reduced feed-to-weight ratio and diarrhea rate (P<0.01). He et al found that the effect of adding 10% fermented rice protein instead of fish meal in the feed was the best, the growth performance of the grouper was improved, the difference was not obvious, and the activities of digestive enzymes in the intestine such as amylase and trypsin were higher than those of the control group , TNF-α, IL-2 and other immune-related genes were down-regulated, and the α diversity of intestinal flora was not significantly different from that of the control group (P>0.05).

5. Existing problems

5.1 Feed remuneration needs to be improved

We have studied immunology and know that the metabolites of microorganisms are antigens. As the animal eats the feed and enters the animal body, it will produce antibodies. When the animal body produces antibodies, it will consume its own energy and protein. At this time, the feed reward will be will decrease.

5.2 Fermentation with loss of feed nutrients

When the feed is disinfected and dried, due to the high temperature, the high temperature will cause the destruction of vitamins and the change of the form and distribution of minerals.

6. Future Vision

As a substitute for antibiotics, bio-fermented feed has attracted the attention of the industry. The feeding effect of bio-fermented feed has been affirmed by the industry, and efforts are being made to study fermented feed. It tends to liquid fermentation, which also shows the maturity of fermentation technology, so we can firmly believe that with the development of animal husbandry, people in the industry will continue to overcome difficulties, develop better fermented feed, and realize antibiotic-free breeding in the true sense. To provide humans with safer and healthier animal products and to achieve human and animal health.