Yeast is a kind of fungus, not the inherent bacteria of human and animal intestines, but can produce a variety of digestive enzymes, which can be metabolized in the digestive tract. Yeast used as probiotics takes the form of living cells, usually yeast cultures. The application of yeast culture in the feed industry has many advantages, because it will not interfere with the effect of antibiotics, but can increase the stability of feed, as a digestive agent also helps to improve the use of nutrients. The effects of yeast feed with different added levels on the intestinal microorganism and immune function of broilers were studied. Adding 1%~2% yeast feed can reduce the number of escherichia coli in feces and cecum chyme and increase the number of lactobacilli. Yeast can improve the utilization rate of phosphorus in non - ruminant livestock. It has been shown that yeast can survive in the back of the alimentary canal and can promote the production of phytase. It was found that the digestibility of phytate phosphate in horses fed yeast additives was improved. He suggested that this activity, together with yeast cultures, could affect phytase activity and increase the absorption of minerals in the hindgut by affecting the microflora in the digestive tract.
As a kind of carotene, it can be used as a forage nutrient fortification agent. Moreover, it has the effect of highly quenching singlet oxygen (1O2) and eliminating free radicals to enhance the body immunity.
The strains currently in use are bacillus and lactobacillus and their mixtures. As the use of antibiotics is limited, the use of this natural feed additive is bound to receive people's attention.
Yeast cell wall
Yeast cell wall is a new, natural, green additives, its products light yellow, powder, no bitterness. It is a special by-product of soluble matter extracted during the production of beer yeast, which accounts for 20% ~ 30% of the dry weight of the whole cell. It plays an important role in maintaining cell morphology and recognition between cells. The active components of yeast cell wall are mainly composed of glucan (57.0%), mannose oligosaccharide (6.6%), glycoprotein (22.0%) and chitin. Other components such as protein, nucleic acid, lipids and ash account for less than 20.0% of its dry weight. Yeast cell wall material is stable during acidolysis, and its fragments can pass through the stomach or rumple intact. Yeast cell wall can be used as an immune booster to improve production performance by stimulating and enhancing the body immunity and improving animal health, especially giving full play to the growth potential of young animals. Its function is mainly played by mannose oligosaccharides and glucan. Mannose oligosaccharides can adsorb pathogenic bacteria in intestinal tract and regulate the non-immune defense mechanism. Activate body fluid and cellular immunity, regulate immune defense mechanism; It has a certain adsorption effect on mycotoxins. Yeast cell wall is suitable for all kinds of animal feed, especially in aquatic animals and weanling pig feed with remarkable effect.
Metal inorganic salts were added to the yeast culture process to enrich metal ions in the form of organic ions in yeast. Yeast cells fortified with minerals combine mineral elements in the form of ions or molecules with the egg white to form stable organisms, eliminating the unique odor of inorganic metal salts. The mineral elements bound by the protein of yeast were more easily absorbed by single stomach and compound stomach than inorganic salt. Organic metal ions bound to protein molecules in yeast cells can be decomposed by rumen microorganisms in the rumen and absorbed by the anterior stomach or directly into the small intestine and hydrolyzed by enteric digestive enzymes. Organic mineral elements in yeast are also more useful than inorganic mineral elements.
At present, the organic trace elements produced by yeast in animal husbandry mainly include chromium and selenium. The results showed that selenium-yeast has the characteristics of low toxicity and good utilization, is rich in nutrition, contains various amino acids and B vitamins, and is the most promising organic selenium source for development and application. Chrome-rich yeast is a kind of yeast cell culture medium containing trivalent chromium, which converts inorganic chromium into organic chromium through biological transformation, so as to improve the absorption efficiency of chromium in organism and reduce its toxic and side effects. It can improve the anti-stress ability of animals, affect the immune response, improve the utilization rate of feed, promote growth, improve the carcass quality, and improve reproductive performance.