Advances in the application of yeast cell walls to ruminants

Yeast cell wall is widely used as an immune booster in animal culture. It can increase the immune level of animals, relieve various stress reactions and adsorb mycotoxin. In recent years, with the deepening of research, the application of yeast polysaccharide in ruminant has been gradually recognized by people. In addition to stimulating the immunity of ruminants, enhancing disease resistance and absorbing mycotoxin, yeast polysaccharide has the function of increasing milk yield and improving milk quality of cows, and has been paid more and more attention by academic circles and breeding industry. This paper introduces the latest research progress in this field at home and abroad, discusses the advantages of yeast cell wall in ruminant application and the future research direction.

Key words: yeast cell wall polysaccharide rumen mycotoxin emulsion protein

In recent years, the abuse of antibiotics has aroused great concern about food safety and environmental hazards. It is urgent to find a safe and effective substitute. The product of polysaccharides based on yeast cell wall is a kind of green, safe and efficient immune booster, which is considered as one of the main methods to replace antibiotics, and has aroused great interest.

It is generally believed that yeast cell wall can stimulate immune function, maintain microecological balance, enhance animal immunity and improve animal health. The production of yeast cell wall products is treated by acid hydrolysis and enzyme hydrolysis, so the acid and enzyme are relatively stable and can be completely passed through the stomach or the stomach, which makes it widely used in different kinds of animals. The application of yeast cell wall in livestock, aquatic animal and so on has been quite mature and stable.

In recent years, with the development of dairy farming, dairy farmers to cow disease, dairy products quality, production performance is more and more attention, the ranch manager has been looking for a good solution, in this opportunity, the yeast cell wall gradually accepted by customer ranch, many farms have the use of yeast cell wall polysaccharides as a necessary means for the cow nutrition regulation.

1. Yeast cell wall

Yeast cell wall is a green nutrient product obtained from Saccharomyces cerevisiae by specific acid and enzymatic hydrolysis. The cell wall of yeast is mainly composed of glucan, mannose oligosaccharide, glycoprotein and chitin. Glucan is mainly composed of D-glucose through 1,3/1,6 bonds, this special structure, can activate macrophages, natural killer cells, T cells and B cells, improve animal disease resistance. Mannose oligosaccharide (MOS) is another important polysaccharide component of yeast cell wall, which has many biological activities. Mannose oligosaccharides are similar to the receptors of many pathogenic bacteria in the intestinal wall of animals. They can bind to pathogenic bacteria, seize the binding site, and adsorb and eliminate intestinal pathogenic bacteria. At the same time, it is also a good probiotics, which can effectively promote the proliferation of beneficial bacteria and regulate the balance of microorganisms in animal body.

2 Mechanism of cell wall action on ruminant in yeast

Polysaccharides products are widely used in dairy cows, common polysaccharides have astragalus polysaccharide, lactose, yeast cell wall polysaccharide and so on.

The mechanism of action of yeast cell wall on dairy cows is more complex than that of livestock, poultry and aquatic animals. As a kind of functional polysaccharide, yeast polysaccharide, part of which is a yeast polysaccharide, combines with mycotoxin in dairy cows' feed through the double helix structure to adsorb mycotoxin and prevent aflatoxin B1 in milk from exceeding the standard. The other part of yeast polysaccharide, degraded by rumen microorganisms, becomes digestible carbohydrate, participates in rumen microbial protein synthesis, promotes milk protein synthesis, and improves milk protein level. There are also some yeast polysaccharides that have not been degraded, along with feed nutrients, enter the intestinal tract, play the role of stimulating immune function in the intestinal tract, improve the body condition of cows, reduce the incidence of cows.

Application of yeast cell walls to ruminants

3.1 Improve immunity and reduce the occurrence of diseases

Nuwman (1993) reported that adding yeast cell walls to the diet of cattle and sheep could enhance disease resistance and prevent diarrhea in calves and lambs. Applied studies on calves showed that the amount of E. coli in the faeces of cows fed with 2 grams of yeast cell wall per day for 5 weeks decreased significantly, and respiratory disease decreased from 9.9% to 3%.

Zhou Yi et al. (2010) added yeast dextran to the diet of calves, which could improve daily weight gain of calves and feed conversion rate. The addition of 75 mg/kg yeast glucan could reduce the incidence of diarrhea and enhance the humoral immune function of calves. The immune function increased linearly with the increase of yeast glucan.

3.2 Regulation of rumen microbial balance

Mannose oligosaccharides (MANnose oligosaccharides) is a good prebiotic. Rumen microorganisms can use mannose oligosaccharides as carbon source to grow and proliferate rapidly. The manna oligosaccharides in the cell wall of yeast are similar to the receptors of many pathogenic bacteria in the intestinal wall of animals, which can bind to pathogenic bacteria, seize the binding site, and adsorb and eliminate intestinal pathogenic bacteria.

According to Zhou Yi et al. (2010), adding yeast cell wall polysaccharide to dairy cow diet can effectively improve the mucosal morphology of the gastrointestinal tract of calves, significantly reduce the number of E. coli in the intestinal tract of calves, and significantly increase the number of lactobacillus in the rectum of calves. It plays a role in regulating microbial balance in the rumen.

3.3 Improve lactation performance and milk quality

Yeast cell wall is also an organic mycotoxin adsorbent. Yeast cell wall is the main component of many toxin adsorbent products. Yeast glucan has a helical molecular structure, and its special configuration can form specific complementary structures with a variety of mycotoxins, thus firmly binding to a variety of mycotoxins (Diaz et al., 2004), and excreting animals through the intestine. In addition, yeast glucan can oxidize phenol oxidase into phenol oxidase by activating the phenol oxidase system, which can specifically degrade mycotoxins in feed, thus playing the role of adsorption and detoxification, avoiding excessive levels of aflatoxin in dairy products and mycotoxin poisoning symptoms in the rumen.

3.4 Improve lactation performance and milk quality

Yeast cell walls are widely used in ruminants because they can improve disease resistance of cows, promote rumen microbial proliferation, and adsorb mycotoxin and pathogenic bacteria. A recent trial reported that yeast cell walls were added to a cow's diet of 50g per day for 55 days, increasing milk production by an average of 14.85% compared to the control group. The milk protein level of cows in the control group increased from 3.1% to 3.2-3.3%, and the average milk fat rate also increased.

4 summary

The application of yeast cell wall in ruminant has been gradually recognized and accepted by people, and some large farms have used it as a conventional raw material in the diet formula. With the in-depth research on the application of yeast polysaccharide in ruminant, the application of yeast cell wall in ruminant will have a broader prospect in the future