Abstract: probiotics are a kind of microbial agents, it is a new feed additive has no toxicity, no side effects, and promote animal growth, improve feed conversion rate, enhance the animal immune function and other characteristics, has been widely used in livestock and poultry breeding. This paper reviews the progress of the research on the action mechanism of probiotics, probiotics, and application in pig production, to provide reference for research and production.
Keywords: probiotics; piglet; production performance; research progress
The development history of 1 probiotics
Probiotics (Probiotic), also known as promoting probiotics, probiotics, and micro ecological regulator, the Chinese name has no uniform provisions on the definition of the interpretation is inconsistent. First, Lilley and Still well in 1965 for the use of the word (Probiotic), probiotics and antibiotics (antibiotic), the role of contradiction. Antibiotics directly kill or inhibit the growth of harmful bacteria. In 1974 the United States RE Parker believes that "probiotics is the balance of intestinal flora of microorganisms and maintain material". In 1989, Fuller was redefined as "a living microbial feed additive that can exert beneficial effects on animals by altering the intestinal microbial balance."". In 1990, H.Sossard is defined as "probiotics to hinder the intake of animal body involved in intestinal microflora, or by enhancing the nonspecific immune function to prevent disease and indirectly play a role in promoting and improving live microbial feed efficiency culture". In 1991, Chinese scholars put forward a more popular concept - "feed microbial additives"".
2 kinds of probiotics
Can be used as a microbial species of probiotics, FDA (1989) allowed feeding 42 kinds of microorganisms. In 1999, 12 species of microorganisms were approved by the Ministry of agriculture, including Bacillus cereus, Bacillus subtilis, fecal streptococci, bifidobacteria, lactobacilli and Streptococcus lactis. Production on the use of probiotics has two kinds: single type bacteria a single genus composition, another for a variety of different bacteria compound bacteria preparation. Generally speaking, the latter can promote the growth of livestock and poultry and improve the utilization ratio of feed. If in accordance with the type of probiotic strains which are used, it can be divided into the following 3 categories:
2.1 lactic acid bacteria
Lactic acid bacteria is a general term for a class of decomposable sugar to produce lactic acid bacteria, the bacteria in the lactobacillus, Bifidobacterium and Streptococcus faecalis is represented. Lactic acid bacteria can synthesize vitamin B, vitamin K, vitamin D and amino acids in the intestine, absorption function can improve the biological activity of mineral elements, improve minerals, and for the host provides essential nutrients, to enhance animal nutrition and metabolism, promoting the growth of organism. Lactic acid bacteria can produce acidic metabolites, the intestinal acidic environment; at the same time, lactic acid bacteria can produce lysozyme and hydrogen peroxide, can inhibit the growth of several potentially pathogenic microorganisms. The main characteristics of this kind of microorganism are as follows: (1) it is the main commensal bacteria of digestive tract of many animals, and can form normal flora. (2) produce lactic acid under micro aerobic or anaerobic conditions, reduce intestinal pH value, and promote the absorption of mineral elements such as vitamin D, calcium, phosphorus and iron. (3) it has strong acid resistance, it can grow at pH 3 to 4.5, and has certain tolerance to the acid environment in the stomach. (4) no high temperature resistance, 5 min treatment at 80, loss of 70% ~ 80%. (5) the production of a specific antibiotic - - - -, which inhibits the growth of Escherichia coli and Salmonella bacteria.
2.2 Bacillus
Bacillus is a kind of aerobic bacteria, which can form spores. In all bacteria, bacillus is the best microbial additive. It has the protease, lipase and amylase activity is high, has the strong degradation capacity of plant carbohydrates. It can quickly enter the intestinal tract after the resurrection, the intestine can consume large amounts of oxygen and maintain intestinal anaerobic environment, inhibit the growth of pathogenic bacteria, maintaining the intestinal normal ecological balance. The main characteristics of this kind of formulation is: (1) with good tolerance, resistant to high temperature (100 DEG C), acid resistance, salt tolerance and granulation process in extrusion resistance, has good stability. (2) producing digestive enzymes with protease, amylase and lipase activities. (3) in the intestinal environment does not proliferate, in the intestinal tract after colonization can consume large amounts of oxygen, maintain intestinal anaerobic environment, and increase intestinal tract aerobic bacteria colonization capacity.
2.3 yeast
Yeast is only found sporadically in the microbial community of the gastrointestinal tract of animals, and the main components of its cell wall are mannan and glucose. Mannan can enhance the activity of phagocytes. The main types of feed yeast are Candida tropicalis, Candida utilis, Saccharomyces cerevisiae, red yeast and so on. The main characteristics are as follows: (1) aerobic bacteria exist in the environment of polysaccharide acid. (2) the body is rich in protein and a variety of B vitamins. (3) without heat resistance, the temperature could be killed at 60 h for 1.

The mechanism of 3 probiotics
The action mechanism of probiotics in theory is also very small, there are 3 main theories: (1) flora theory; (2) bacteria barrier theory; (3) from microbial oxygen theory. Probiotics is mainly through the following ways to play its role in animal body.
3.1, supplement the beneficial flora, improve the flora balance of the digestive tract, prevent and treat the flora disturbance
There are a lot of animal digestive tract bacteria, some bacteria can effectively promote the growth and digestibility of livestock and poultry, called probiotics; some bacteria can inhibit the growth and pathogenicity, known as harmful bacteria. Under normal circumstances, these bacteria in the digestive tract of livestock and poultry have maintained a good balance, maintain the normal growth and production of livestock and poultry, these bacteria once lost balance, cause digestive function disorder, inhibition of growth and development, is a serious disease.
3.2 stimulate the immune system and improve the immunity of the organism
The probiotics are beneficial bacteria should be a good immune activator, can effectively improve the activity of macrophages, enhance the phagocytosis activity by stimulating the immune antibody production and stimulate humoral immunity and cellular immunity, to enhance immunity and disease resistance.
3.3 participate in the competition and help the body eliminate toxins and metabolites
In the digestive tract probiotics survival and reproduction of spatial competition, between bacteria and pathogenic bacteria, to settle time competition site and nutrition competition competition, restrict the survival and reproduction of pathogenic bacteria. There are bacteria generate dense membrane flora in the digestive tract, the formation of a microbial barrier, inhibiting gastrointestinal adhesion of pathogenic bacteria, and toxic products; on the other hand to prevent the absorption of toxins or waste.
3.4, improve the body metabolism, supplement the body nutrients, and promote livestock and poultry growth
Probiotics can reproduce the beneficial bacteria in the digestive tract, can promote the absorption and utilization of effective synthesis in the digestive tract of a variety of amino acids, vitamins and a series of nutritional components, so as to promote animal growth and weight gain.
Application of 4 probiotics in pig production
Application of 4.1 in prevention of diarrhea in piglets
Piglet diarrhea is one of the most important diseases that plagued the piglets. It is reported that under normal circumstances, the incidence of mild cases is 10% to 20%, serious can reach 40% ~ 50%, and some even reach 100%. At the same time, the mortality rate of piglets caused by the disease is also quite high, generally in the 10% to 30%, serious can reach more than 50%.
Zhao Jingyang (2001) of liquid probiotics and enzyme of probiotics on piglets daily gain, diarrhea rate and survival rate, the results showed that the experimental group added 0.75% enzyme probiotics, piglets weight gain compared with the control group increased 15.94% (P > 0.01); and the diarrhea rate was lower than the control group (P < 8.92% 0.05). The test results show that the early inoculation of suckling piglets and feed with probiotics and enzyme probiotic supplements can significantly improve the piglet's weight, reduce the piglets diarrhea rate, improve the survival rate of piglets. Liu Tao (2003) studies show that the addition of Gln in weaned piglets weaned piglets can promote intestinal development, alleviate weaning stress, reduce diarrhea rate, improve growth performance and immunity of weaned piglets. Huang Guanqing (2008) found in weaning piglets (21d 1 ~ Ala-Gln after weaning) diets supplemented with 0.1% 10d in 10~20; or in post weaning dietary D in the addition of 0.3% Ala-Gln could significantly improve the weight gain of piglets, suggesting that early weaned piglets supplemented with exogenous Ala-Gln can promote the growth and development.
The application of 4.2 in the performance of piglets
The micro ecological environment of probiotics can improve piglet gastrointestinal tract, so as to ensure that the animal has good digestibility and utilization of feed, and then get a good feeding effect. Yin Zhaohua (2008) found that, compared with the control group, weaned piglets in 35 ~ 50 days of age, the addition of solid and liquid EM EM average daily gain were increased by 25% and 36%, and the gain of the test group and the control group there was a significant difference between the weight; the feed weight ratio were decreased by 13% and 19%, each there was no significant difference between. Weaned piglets were in the 51~68 day old stage, but there was no significant difference in performance between the experimental group and the control group. Liang Mingzhen (2002) found that adding 0.2% probiotics in weaned piglets, the weight gain of piglets increased 4.6%, feed utilization rate increased by 5.7%. Zhao Jingyang (2001) also showed that probiotics can make the piglets daily gain increased by 15.94 (P < 0.01), weaning weight gain of piglets increased 8.75%.

4.3 application in sow performance
Research shows that adding activated folic acid 3 mg/kg in 3 and grew up long multiparous parity sow diets, increase litter size 7.43%, live farrowing rate increased by 8.5% and the birth weight of the piglets increased 10.61%. Yao Yuan et al. (2008) found that adding yeast culture to the diets of sows could significantly increase the average weaning weight of piglets (P < 0.05). Inteross reported, adding probiotics in sow diets, the number of weaned piglets and piglets weaning weight was significantly higher than the group without added. Podson and other 20 sows were fed with Bacillus subtilis preparation, the average number of weaned piglets was 9.05, and the weight of weaning piglets was 5.48kg, which was 5.85% and 3.40% higher than that of the control group, respectively. Williams pointed out that the addition of probiotics in sow diets can stimulate the sows in small and large end of fermentation, thereby increasing volatile fatty acid and bacterial fermentation end product yield, provide more energy for sows, sows is conducive to nutrient utilization and milk production, and thus improve the weaning weight of piglets and piglets weaned at age shortened weight.
The problems and research directions of 5 probiotics are
(1) has been confirmed for a probiotic strain is less, the need to develop new species, can also use the method of molecular biology, the transformation of existing strains, which has the required performance.
(2) in view of the current progress in research on the mechanism of action of probiotics is slow, the urgent need to strengthen the power mechanism of probiotics for more in-depth research, production and development, guiding the use of probiotics.
(3) improve the study of live bacteria concentration, dosage of probiotics to improve microbial tolerance to adverse environment, prolong the storage period of products.
(4) there are still some probiotics product quality is not stable, production is mixed, imitation stage, detection means perfect, product standards and testing methods are still on the market confusion caused by probiotics products hardly identification. Therefore, it is necessary to establish a perfect testing standard for the industry and formulate rules for the implementation of relevant laws and regulations so as to standardize production and publicity.
(5) the improper use of the phenomenon still exists, to a certain extent influence the effect of the use and development of scientific research of probiotics, probiotics usage requirements are also increasingly urgent.
From: China veterinary medicine 114 nets
Chuang Xin Liu teacher