The use of feed antibiotics is considered to be the greatest biotechnology for livestock production in the twentieth century. It refers to antibiotics used in feeds to protect animal health, promote animal growth and production, and improve feed utilization efficiency. . Since Moore et al. discovered in 1946 that the addition of streptavines to feeds can significantly increase the growth rate of broilers, antibiotics began to be used as feed additives and were widely used in feeds, along with the industrialization of antibiotic production and the scale of the aquaculture industry. Antibiotics play a huge role in preventing and treating animal diseases, increasing the productivity of livestock and poultry, and meeting the needs of human animal products. However, the abuse of antibiotics in recent years has also brought more and more problems to human beings. Many countries and international organizations have banned the use of antibiotic feed additives due to the increasing danger of bacterial resistance, drug residues in animal products, and allergic reactions. In recent years, China’s regulations in this area have become more and more strict. With the promulgation and implementation of these restrictions and regulations, regardless of feed enterprises or farms, attitudes or measures for “diseases†need to be changed from “treatment†to “Prevention†is looking for new feed additives or methods to replace feed antibiotics. First, the mechanism of the role of antibiotics The first step in finding alternatives to antibiotics is to understand the mechanism of action. The following is a summary of the mechanism of action of antibiotics in order to provide input for finding suitable antibiotic alternatives. 1, adjust the intestinal microbes Antibiotics achieve growth-promoting effects through the influence of intestinal micro-organisms, and current research suggests that they are mainly reflected in three main aspects. 1) The most direct and direct effect of antibiotics is sterilization and disease prevention. Antibiotics can inhibit or kill certain pathogenic microorganisms in the intestinal tract of animals, which can reduce the symptoms of clinical and subclinical infection caused by pathogenic bacteria; 2) Antibiotics may promote animal growth by inhibiting the utilization of nutrients by gastrointestinal microorganisms in animals. The most powerful evidence for this hypothesis is that feed antibiotics do not exhibit growth-promoting effects in sterile animals, whereas oral administration of normal intestinal flora to sterile animals inhibits their growth and inhibits growth after feeding penicillin. Moreover, the effect of feeding antibiotics on animals with more gastrointestinal microbes is more obvious. By inhibiting the growth of intestinal microbes, antibiotics reduce the maintenance loss of nutrients in the gastrointestinal tract, thereby promoting the growth of animals. 3) Inhibition of intestinal microbes to produce harmful metabolites. Microorganisms in the gut can degrade to produce ammonia, toxic phenols and aromatic compounds through the use of nutrients in the intestines, reduce the production of ammonia by intestinal microbes, and inhibit phenolic compounds, which may be a potential mechanism for antibiotic growth. 2, promote the absorption of nutrients Certain antibiotics can significantly thin the intestinal wall of the animal and increase the permeability of the intestinal mucosa, thereby facilitating the permeability and absorption of nutrients by the intestinal wall and improving the utilization rate of the feed. In addition, studies have shown that antibiotics can reduce the maintenance of intestinal tract, slow down the rate of intestinal epithelial cell renewal, and ultimately promote growth. 3, the immunological mechanism of antibiotic action In the process of immune reaction, the animal body will reduce the feed intake of the animal, increase the maintenance needs of the body, and accelerate the degradation of the body protein, resulting in a decrease in the utilization rate of the animal feed, thereby inhibiting the growth of the animal. Numerous studies have shown that most of the antibiotics used for feeding have immunosuppressive effects. Although the specific mechanism of immune regulation is still unclear, feeding antibiotics generally affect the immune system by directly (directly affecting the immune system's ability to respond) or indirectly (by reducing the intensity of microbial invasion), thereby preventing the immune system from activating. Promote animal growth (as shown below). Second, the nutritional strategy of antibiotic replacement Judging from the mechanism of antibiotic growth, the main part of antibiotics is in the intestine, and antibiotic substitutes should have at least three functional characteristics in order to achieve the effect of replacing antibiotics: 1) adjust intestinal microbial structure; 2) To ensure the animal's intestinal health, promote the absorption of nutrients; 3) enhance intestinal immunity, improve animal disease resistance. These effects are interrelated and they are all directly related to gut health. Therefore, no matter what mode of action, the goal of antibiotic substitutes is very clear, that is, to ensure the intestinal health of animals. In the following content, we will first briefly review the structure and function of the intestines, the physiological characteristics of the piglets, and then propose the antibiotic alternative nutrition strategy of the farmers. 1, the structure and function of the intestines 1) Structure Regardless of the animal, the basic composition of the intestine is similar, including the small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum). The small intestine is the main part of digestion and absorption, each with certain organizational characteristics. Small intestinal mucosa, especially the jejunum, has many annular folds and villi and microvilli (see Figure 2), which greatly enlarges the surface area of ​​the mucosa and is beneficial to the digestion and absorption of nutrients. 2) Function With the deepening of research, it has been found that the intestine is not only an important nutrient for the body to digest and absorb organs, but also an important immune and endocrine organ in the body. More importantly, it has a barrier function - it can prevent toxins in the intestinal lumen. Harmful substances such as bacteria and anti-nutritional factors enter the body and cause damage to the body. Intestinal barrier refers to the sum of the structure and function of the intestine to prevent harmful substances (bacteria and toxins, etc.) in the intestinal lumen from entering the other tissues and organs and blood circulation in the body, mainly including four kinds (see Figure 3): Mechanical Barriers, biological barriers, chemical barriers, immune barriers. The maintenance of normal intestinal barrier function depends on intestinal mucosa epithelium, normal intestinal flora, intestinal secretions, peristalsis, intestinal related immune cells, and the like. The intestinal mucosal barrier is most important with a physical barrier based on the tight junctions between intact intestinal mucosal epithelial cells and epithelial cells (Vicente et al., 2001). 2, the physiological characteristics of the piglets 1) development of the digestive tract 2) Insufficient gastric acid secretion 3) Digestive enzyme secretion and activity are constantly changing 4) The immune system is gradually improving. 5) Digestive tract microbial flora to be perfected and stabilized Due to the above-mentioned special physiological characteristics in the stage of suckling pigs, coupled with the influence of breeding management, disease prevention and control, etc., the piglets in actual breeding will inevitably have intestinal damage. 3, nutritional strategy to replace antibiotics At present, common additive products on the market, such as enzyme preparations and acidifiers, are mainly used to improve the ability of animals to digest nutrients; probiotics, acid preparations, etc. to regulate intestinal microflora structure as the main function; Immune-functional plant extracts/plant essential oils and other products. In addition, there are some new additive products on the market, such as egg yolk antibodies, phage, etc., which are being promoted. However, based on the stability, remarkable effect and low cost of use of antibiotics in sterilization, disease prevention, growth promotion, so far, no single product can completely replace antibiotics and the effect is recognized. Therefore, the replacement of antibiotics requires "strategic" thinking. The idea of ​​the “replacement strategy†of the US and the peasants is: systematic thinking and key breakthroughs! Firstly, based on the physiological characteristics of the animals, based on the feed itself, the feed is well prepared with the idea of ​​precise nutrition (nutrition level, raw material selection, processing technology, etc.). At the same time, attention is paid to the health of the digestive tract of animals, especially intestinal health. In the aspect of intestinal health, it is necessary to ensure the integrity of the intestinal structure and the normal barrier function by rational use of additive products. 1) Mechanical barrier The intestinal mechanical barrier is mainly composed of intestinal epithelial cells, epithelial lamina propria, and cell junctions on the lateral side of epithelial cells (Reynolds et al., 1996). Intestinal epithelial cells are an important part of the intestinal mucosal barrier. There are two main aspects of intestinal epithelial function: 1) it is an important barrier to prevent exogenous substances, bacteria and endotoxin from entering the intestine (Blikslager et al., 2007); 2) she is a selective filter and can choose Sexually allows essential nutrients, electrolytes and water to enter the systemic circulation from the intestinal lumen (Broer et al. 2008). For this barrier, the provision of energy is paramount. On the one hand, intestinal mucosa itself requires a lot of energy to maintain its normal function. On the other hand, when the body is stimulated, intestinal mucosal cells are most vulnerable to damage, and its repair also requires a lot of energy. Therefore, substances that can rapidly supply energy to the intestinal mucosa are important measures to protect the intestinal mechanical barrier intact or to ensure rapid repair after injury. Butyric acid products (sodium butyrate, glyceryl butyrate, etc.) and glutamine are the best choices. 2) Biological barrier The normal flora on the intestinal mucosa constitutes a biological barrier to the gut. The normal flora is a group of bacteria that are designated to live in the intestines and are generally beneficial to animals. Some scholars have pointed out that heat stress causes intestinal villus damage is the main cause of poor absorption of feed nutrients, and it is believed that the utilization efficiency of feed during heat stress is closely related to the degree of damage of intestinal villi. Among them, the "deep layer", that is, the flora closely adhering to the mucosal surface of the intestine, forming a bacterial biofilm with the mucosal epithelium, mainly Lactobacillus and Bifidobacteria, are the two most physiologically important bacterial groups in the intestine. For this layer of barrier, any substance that promotes the growth of beneficial bacteria in the intestine and inhibits harmful bacteria is the first choice. Acid preparations, microecological preparations, probiotics, and the like can all exert the above functions through direct or indirect routes. 3) immune barrier The intestine is one of the largest immune organs in the human body. According to function and distribution, the intestinal mucosal immune system can be divided into gut-associated lymphoid tissue (GALT) and diffuse immune cells. The intestinal-associated lymphoid tissue mainly refers to the collecting lymphoid nodules distributed in the intestine, that is, the Peyer's section, which is the induction and activation site of the immune response; the diffuse immune cells are the effect sites of intestinal mucosal immunity. For this barrier, the additive products we choose must have immune-enhancing or immunomodulatory effects, usually plant essential oils/plant extracts, yeast and their derivatives. Third, the conclusion For the four-layer barrier of the intestine, a targeted selection of products is required to better function; at the same time, the four layers of the intestinal barrier are not independent of each other, and there is also an interaction effect between them, so the additive product is selected. When you need system thinking, the solution is solved. In addition, factors affecting the use of products (including feeds and additives) include pig farm conditions, feeding management, and disease control. Therefore, while providing products and solutions, we must provide corresponding services as a guarantee. Only in this way can the goal of "replacement" be finally achieved. Outdoor Wpc Flooring,Wpc Wood Plastic Composite Plank Flooring,Wpc Wood Grain Flooring,Wpc Deck Panel Flooring Shandong Zeen Decoration Materia.Co., Ltd. , https://www.zeendecor.com
Antibiotic replacement strategy in the post-antibiotic era