Research progress of probiotics and its application in pig production Wang Xiu 1, Wang Jizhong 2 1. Shandong Wudi County Animal Husbandry and Veterinary Bureau; 2. Shandong Wudi County Agricultural Bureau 1 Development history of probiotics Probiotics, also known as somatotropins, bacteriostatic agents, live bacterial preparations, and micro-ecological regulators, have no uniform definition of Chinese names, and their definitions are not consistent. First, Lilley and Still Well used the term probiotics in 1965, which is contradictory to antibiotics. Antibiotics directly kill or inhibit the growth of harmful bacteria. In 1974, RE Parker of the United States believed that "probiotics are microorganisms or substances that maintain the balance of the intestinal flora." In 1989, Fuller was redefined as "a living microbial feed additive that can exert a beneficial effect on animals by altering the balance of intestinal microbes." In 1990, H. Sossard defined probiotics as "inhibiting the involvement of intestinal microbial communities in animals, or inducing non-specific immune functions to prevent disease, indirectly promoting and improving feed efficiency. Things." In 1991, Chinese scholars proposed a more common concept - "feeding microbial additives." 2 Types of probiotics There are many types of microorganisms that can be used as probiotics, and the US FDA has allowed 42 kinds of microorganisms to be fed. There are 12 kinds of microbial species approved by the Ministry of Agriculture in 1999, including Bacillus cereus, Bacillus subtilis, Streptococcus faecalis, Bifidobacterium, Lactobacillus and Streptococcus lacticus. There are two kinds of probiotics used in production: one single-type bacterial preparation composed of a single genus, and the other is a composite bacterial preparation composed of a plurality of different genus. In general, the latter is more capable of promoting livestock growth and improving feed utilization than the former. According to the type of strain used by probiotics, it can be divided into the following three categories. 2.1 lactic acid bacteria Lactic acid bacteria are a general term for a class of bacteria which can decompose sugars to produce lactic acid, and the beneficial bacteria are represented by Lactobacillus, Bifidobacterium and Streptococcus. Lactic acid bacteria can synthesize B vitamins, vitamin K, vitamin D and amino acids in the intestines, improve the biological activity of mineral elements, improve the absorption function of minerals, and provide essential nutrients for the host to enhance animals. Nutritional metabolism, promote the growth of the body. Lactic acid bacteria can also produce acidic metabolites, making the intestinal environment acidic. At the same time, lactic acid bacteria can also produce lysozyme and hydrogen peroxide, which can inhibit the growth of several potential pathogenic microorganisms. The main characteristics of these microorganisms are: the main symbiotic bacteria of various animal digestive tracts, which can form normal flora; produce lactic acid under micro-oxygen or anaerobic conditions, lower intestinal pH value, promote vitamin D, calcium, phosphorus and Absorption of mineral elements such as iron; strong acid resistance, can still grow at pH 3.0~4.5, and has certain tolerance to acidic environment in stomach; not resistant to high temperature, treated at 80 °C for 5 min, loss 70 % ~ 80%; the production of a special antibiotic - acid bacteria, can effectively inhibit the growth of E. coli and Salmonella. 2.2 Bacillus Bacillus is an aerobic bacterium that forms endospores, and Bacillus is the most ideal microbial additive in all genus. It has high protease, lipase and amylase activity, and has strong degradation ability to plant carbohydrates. It can be revived quickly after entering the intestine, which can consume a lot of oxygen in the intestine and maintain the intestinal anaerobic environment. It inhibits the growth of pathogenic bacteria and maintains the normal ecological balance of the intestines. The main features of these preparations are: good tolerance, high temperature resistance (100 ° C), acid and salt resistance, and resistance to extrusion during granulation. It has good stability; produces digestive enzymes with protease, amylase and fat. Enzyme activity; does not proliferate in the intestinal environment, can consume a large amount of oxygen after colonization in the intestine, maintain the intestinal anaerobic environment, and increase the colonization ability of the intestinal aerobic bacteria. 2.3 Yeast Yeast is only sporadically present in the microbial community of the gastrointestinal tract of animals. The main components of the cell wall are mannan and glucose, and mannan can enhance the activity of phagocytic cells. The types of feed yeast mainly include Candida tropicalis, Candida utilis, brewer's yeast, and red yeast. The main features are: aerobic bacteria, present in the acid-poor environment of the polysaccharide; the body is rich in protein and a variety of B vitamins; not heat-resistant, the temperature can be killed in the temperature of 60 ° C ~ 70 ° C, 1 h. 3 Mechanism of action of probiotics The theoretical progress of the mechanism of probiotics is still very small. At present, there are mainly three theories: dominant flora theory; microbial barrier theory; microbial oxygenation theory. Probiotics mainly play their role in animals through the following pathways. 3.1 Supplementing beneficial bacteria, improving the balance of digestive flora, preventing and treating dysbacteriosis There are a large number of microbial flora in the digestive tract of livestock and poultry, some of which can effectively promote the growth of livestock and poultry and feed digestion, which is called beneficial bacteria; some microflora have the effect of inhibiting growth and pathogenesis, called harmful bacteria. Under normal circumstances, these flora in the digestive tract of livestock and poultry maintain a good balance, maintaining the normal growth and production of livestock and poultry. Once these flora loses balance, it causes digestive disorders, inhibits growth and development, and serious Can cure diseases. 3.2 Stimulate the body's immune system and improve the body's immunity. The beneficial bacteria in probiotics are good immune activators, which can effectively increase the activity of macrophages, stimulate immunity by producing antibodies and enhance phage activity, stimulate body humor immunity and cellular immunity, and lead to immunity. And the enhancement of disease resistance. 3.3 Participate in the survival of the flora, assist the body to eliminate toxins and metabolites Probiotics participate in the survival and reproduction space competition between the beneficial bacteria and pathogenic bacteria in the digestive tract, time competition, competition in settlements and nutrition competition, and limit the survival and reproduction of pathogenic bacteria. The beneficial bacteria form a dense membrane flora in the digestive tract, forming a microbial barrier, inhibiting the adhesion pathogens in the digestive tract and neutralizing the toxic products; on the other hand, preventing the absorption of toxins or wastes. 3.4 Improve the body's metabolism, supplement the body's nutrients, and promote the growth of livestock and poultry The beneficial bacteria of probiotics can be propagated in the digestive tract, which can promote the effective synthesis, absorption and utilization of a variety of amino acids and vitamins in the digestive tract, thereby promoting the growth and weight gain of livestock and poultry. 4 Probiotics in pig production 4.1 Application in preventing piglet diarrhea Piglet diarrhea is one of the most important diseases that plague piglets. According to reports, under normal circumstances, the incidence is 10% to 20%, and severe cases can reach 40% to 50%, and some even reach 100%. At the same time, the mortality rate of piglets caused by the disease is also quite high, generally between 10% and 30%, and severely up to 50%. Zhao Jingyang studied the effects of liquid probiotics and enzyme-probiotics on daily weight gain, diarrhea rate and survival rate of suckling pigs. It was found that the daily weight gain of suckling piglets increased by 15.94% compared with the control group in the test group supplemented with 0.75% enzyme-probiotics. (P>0.01); the diarrhea rate was 8.92% lower than the control group (P<0.05). The results showed that early inoculation of probiotics in lactating piglets and feed supplemented with enzyme-probiotics could significantly increase the daily gain of suckling piglets, reduce the diarrhea rate of suckling piglets, and improve the survival rate of suckling piglets. Liu Tao and other studies have shown that adding proper amount of Gln to the diet of weaned piglets can promote the intestinal development of weaned piglets, relieve the stress of weaning, reduce the rate of diarrhea, and improve the growth performance and immunity of weaned piglets. Huang Guanqing and other studies found that 0.1% Ala-Gln was added to the diet within 1d to 10d after weaning (21d weaning), or 0.3% Ala-Gln was added to the diet within 10d to 20d after weaning. Increasing the daily weight gain of piglets suggests that early weaned piglets supplemented with exogenous Ala-Gln can promote their growth and development. 4.2 Application in piglet production performance Probiotics can improve the micro-ecological environment of the gastrointestinal tract of piglets, so as to ensure that the animals have good digestibility and utilization rate of the feed, and thus obtain good feeding effect. Yin Zhaohua's study found that compared with the control group, the average daily gain of solid EM and liquid EM increased by 25% and 36% in the weaned piglets from 35 days to 50 days, respectively, and the day between the experimental group and the control group. There was a significant difference in weight gain; the feed-to-weight ratio was reduced by 13% and 19%, respectively, and the difference between the groups was not significant. The performance of the weaned pigs between the test group and the control group was not significant at the age of 51 days to 68 days. Liang Mingzhen found that adding 0.2% probiotics to the diet of weaned piglets increased the daily weight gain of piglets by 4.6% and the feed utilization rate by 5.7%. Zhao Jingyang also proved that probiotics could increase the daily gain of suckling piglets by 15.94 (P<0.01) and increase the daily gain of weaned piglets by 8.75%. 4.3 Application in sow production performance Studies have shown that 3 mg/kg of active folic acid is added to the diet of 3 sows growing up and growing long, the litter size of sows is increased by 7.43%, the live birth rate is increased by 8.5%, and the birth weight of piglets is increased by 10.61%. . Yao Yuan et al (2008) found that adding yeast culture to sow diets significantly increased the average weaned individual weight of piglets (P<0.05). Inteross et al reported that the addition of probiotics to the sow diet resulted in significantly higher weaned piglets and piglet weaning weight than the non-added group. Podson et al. added Bacillus subtilis to 20 sows. The average number of weaned pigs was 9.05, and the weaned pigs weighed 5.48 kg, which was 5.85% and 3.40% higher than the control group. Williams pointed out that the addition of probiotics to sow diets can stimulate the back-feeding of the small intestine and large intestine of sows, thereby increasing the production of volatile fatty acids and bacterial end products, providing more energy to the sows and benefiting the sows. Nutrient utilization and milk production, thereby increasing the weaning weight of piglets and shortening the age at which piglets reach weaning weight. 5 Probiotics problems and research directions 5.1 At present, it has been confirmed that there are few strains suitable for probiotics, new strains need to be developed, and existing strains can be modified by molecular biology to have the required properties. 5.2 In view of the current slow progress in the study of the mechanism of action of probiotics, it is urgent to strengthen the research on the mechanism of action of probiotics to guide the development, production and use of probiotics. 5.3 Strengthen research on probiotics dosage forms, increase the concentration of live bacteria, increase the tolerance of microbial agents to adverse environments, and extend the shelf life of products. 5.4 There are still some probiotic products whose quality is unstable, production is in the stage of compounding and imitation, and the testing methods are not perfect. The standards and testing methods of the products are still confusing, which makes the probiotic products on the market difficult to distinguish. Therefore, it is necessary to establish sound industry testing standards, formulate detailed implementation rules for relevant laws and regulations, and standardize production and publicity. 5.5 The improper use of the phenomenon still exists, which affects the use effect and development of probiotics to a certain extent, and the requirements for the study of the use of probiotics are becoming more and more urgent.
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Research progress of probiotics and its application in pig production