Key words: animal microecological preparation research progress mechanism mechanism application prospect development trend
The problem of antibiotic abuse in feed has become increasingly prominent, causing the disease resistance of farmed animals to decrease, the resistance of pathogenic bacteria to increase, drug residues in products, and food safety hazards seriously restricting the development of aquaculture. At present, the restrictions on the use of antibiotics in western developed countries are becoming more and more strict, and stricter requirements are imposed on the restrictions on drug residues in animal products exported from China. In particular, the detection of antibiotic residues in animal-derived foods has become a world meat trade. One of the important technical indicators and technical barriers. Therefore, it is urgent to develop and apply new feed additives without drug residues.
The development and utilization of microecological preparations have solved the above problems. Microecological preparation, also known as probiotics, bacteriostatic agents, somatotropin, probiotics, and live bacteria preparations, is a preparation of active microorganisms, metabolites and growth-promoting substances beneficial to the host under the guidance of microbiology theory. . Microecological preparations use the relationship between mutual antagonism, symbiosis and mutual growth of microorganisms, as well as the acid production, degradation of proteins, decomposition of sugars and fats, degradation of NH3 and H2S, and the inhibition of pathogenic microorganisms and decomposition of feeds. The medium protein is a polypeptide or an amino acid, which degrades residual ammonia nitrogen and nitrite in water. It is a natural biologically active preparation with no toxic side effects, no drug resistance, no drug residues, and regulates the maintenance of micro-ecological balance in the gastrointestinal tract by promoting the growth of beneficial microorganisms in the intestine and inhibiting the growth and reproduction of harmful microorganisms. Achieve disease prevention and promote growth. At the same time, these microorganisms can also produce growth-promoting factors, a variety of digestive enzymes and vitamins, thereby promoting the digestion and absorption of nutrients and the growth and reproduction of animals. In addition, these microorganisms can also produce immunoregulatory substances such as immunoregulatory factors and interferons, stimulate the growth and development of intestinal immune organs, enhance the body's immunity, and prevent various diseases. It is a new type of green environmental protection drug. Replace antibiotics.
The earliest research and application of livestock and poultry microecological preparations can be traced back to 1947. Monhard first discovered that feeding piglets with Lactobacillus can effectively increase the weight of piglets and improve the health of piglets. In the 1970s, the United States took the lead in using microecological preparations, and the effect was very obvious, showing the advantages that antibiotics could not match. In the 1980s, microecological preparations began to spread around the world and gradually became recognized by the world. Especially in the past decade, the development of microecological preparations has been particularly rapid. The US FDA stipulates that there are 42 microorganisms allowed to be used as prebiotics. The feed-grade microbial additive strains that can be directly fed to animals published by the Ministry of Agriculture (2003) include 15 species such as Bacillus subtilis, Lactobacillus casei, Lactobacillus lactis, Bacillus cereus, Lactobacillus and yeast.
The ideal microecological preparation strain should have the following characteristics:
1 is harmless to the host and does not cross with pathogenic microorganisms;
2 Strong tolerance to bile and strong acid;
3 The fermentation process produces inhibitory substances and metabolites such as lactic acid;
4 easy to proliferate in the body;
5 There is still high survival rate after processing;
6 Even if mixed in the feed at room temperature, it will survive for a long time.
1 Classification of animal microecological preparations
Broadly speaking, microecological preparations include animal microecological preparations and plant microecological preparations. Animal microecological preparations include both normal microbial members, especially live bacterial preparations of dominant populations, and preparations prepared by substances that promote the growth and reproduction of normal microbial populations, which can produce certain biological or growth effects, such as probiotics. yuan.
There are many classification methods for animal microecological preparations, but the commonly used classifications are as follows:
1.1 According to the types of strains used in microecological preparations, they are mainly divided into two categories: single fungi and composite microecological preparations. The single fungal microecological preparations include the following four types:
1.1.1 Lactic acid fungi micro-ecological preparations mainly include Lactobacillus acidophilus, Lactobacillus brevis and Streptococcus faecalis. It is a Gram-positive bacterium that can decompose sugar to produce lactic acid, anaerobic or facultative anaerobic growth. Lactic acid bacteria play a decisive role in maintaining the stability of the normal microflora of the digestive tract. The disadvantage is that most of the lactic acid bacteria have poor heat resistance, which may lead to unstable product quality and thus affect the feeding effect. According to reports, lactic acid bacteria are not resistant to high temperature. After treatment at 80 ° C for 5 min, the loss will be 70% to 80%; but acid resistance, can grow at pH 3.0 ~ 4.5, and has certain tolerance to the acidic environment in the stomach. In the animal body, the pH is lowered by biological antagonism to prevent and inhibit the invasion and colonization of pathogenic bacteria; the harmful substances such as ammonia, sputum and skatole are degraded to maintain the normal ecological balance in the intestinal tract; the living cells and their metabolites are more High superoxide dismutase (SOD) can eliminate the adverse effects of oxygen free radicals and enhance humoral and cellular immunity. Studies have found that lactic acid bacteria colonize the intestines of fish, can resist Gram-negative pathogenic bacteria, enhance anti-infective ability, increase the immunomodulatory activity of intestinal mucosa, and promote growth. Lactic acid bacteria can be used in feed for lactating and weaning animals.
1.1.2 Bacillus microecological preparations are mainly Bacillus licheniformis, Bacillus subtilis, Bacillus cereus, Bacillus natto, etc., which are aerobic bacteria. Spores are produced under certain conditions. Due to the special structure of spores, Bacillus has strong resistance to dry, high temperature and high pressure, oxidation, strong acid and alkali, extrusion and other adverse environments. The product has high stability and strong protease. Lipase and amylase activities have various effective enzymatic effects in germination and growth in the intestine.
1.1.3 Yeast micro-ecological preparations mainly include brewer's yeast, Candida utilis, Saccharomyces cerevisiae, red yeast, etc. Yeast cells are rich in protein, nucleic acid, vitamins and various enzymes, which enhance animal immunity and increase feed palatability. It can promote the animal's ability to digest and absorb feed, and can improve the utilization of phosphorus by animals. It can be used to ferment and produce feed single-cell protein.
1.1.4 Photosynthetic bacteria microecological preparations are a kind of heterotrophic microorganisms with photosynthesis ability. They mainly use small molecular organic compounds to synthesize various nutrients needed for their own growth and reproduction, rich in protein, B vitamins, coenzyme Q, and anti-activity. A variety of biologically active substances such as viral factors, and natural pigments such as carotenoids and lycopene. The content of various essential amino acids in the photosynthetic bacterial cell protein is higher than that of the yeast. Photosynthetic bacteria have a good effect in improving the water environment, promoting the growth of aquatic animals, and improving color.
1.1.5 Composite microecological preparations Compared with the first four microecological preparations consisting of a single strain, the composite microecological preparation is prepared by compounding a plurality of bacteria according to a certain ratio, and can adapt to various conditions and hosts, and has disease prevention. It can cure diseases, promote growth, and improve feed conversion rate.
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