The problem of drug residues caused by the application of antibiotics in feed and the widespread concern of the society for safe feed have prompted researchers to develop a new type of non-antibiotic or “natural†feed additive. Yeast culture (YC) is an antibiotic substitute. In recent years, there have been many reports on its application in dairy production, and it has been shown that adding yeast culture to the diet can stabilize the rumen environment and promote beneficial bacteria. The proliferation of the group can also increase the feed intake and anti-stress ability of the cows. 1 Brief Yeast culture is a liquid, solid secondary fermentation controlled by strict conditions or directly processed in a solid medium, together with the medium, containing yeast and its growth medium and yeast metabolites, nutrition Rich, crude protein content of 30%-60%, rich in essential amino acids, less calcium, high phosphorus and potassium content, rich in B vitamins. 2 Effect of yeast culture on production performance Yeast culture can improve the rumen environment, improve the performance of dairy cows, and reduce the number of somatic cells and improve the quality of milk. In 2010, Wang Xiaohong and others used a composite yeast culture for dairy cow feeding experiments. The results showed that compared with the blank control group, the daily milk yield of the experimental group increased by 1.07kg/head (P>0.05), the number of somatic cells decreased by 10%, and the milk fat percentage increased by 16.5% (P>0.05). It is indicated that the composite yeast culture has a good effect in increasing milk production and reducing the number of somatic cells in dairy cows. In 2010, Hippen AR and other 16 Holstein lactating cows were used as experimental animals to study the effects of distiller's protein feed (DDGS) and Yikang XP on dairy performance. The results showed that Yikang XP can positively affect the performance of dairy cows regardless of whether DDGS is added to the dairy diet. If the diet contains 20% DDGS, Yikang XP can not reduce the decline of milk fat percentage. When adding DDGS to lactating cow diets, special attention should be paid to the reasonable amount of effective fiber to maintain milk fat production. 3 The effect of yeast culture on immune function As a precursor of living bacteria, the yeast culture has enhanced its reproduction and vitality after entering the gastrointestinal tract. It can effectively inhibit the proliferation of pathogenic microorganisms, participate in the survival competition of pathogenic microbial flora, and reject the adsorption and colonization of pathogenic bacteria on the surface of intestinal mucosa to assist the elimination of the body. Toxins and their metabolites prevent the absorption of toxins and wastes, enhance the body's immunity and disease resistance, and play a role in the prevention and treatment of dairy cow digestive diseases. In 2006, Lu Chunlian and others added the yeast culture Yikang XP to the dairy cow diet at the beginning of lactation at a dose of 60g per day. The results showed that the incidence of dairy cows in the experimental group was significantly lower than that of the control group, indicating that Yikang XP has the effect of preventing the occurrence of dairy disease. 4 Effect of yeast culture on rumen fermentation The addition of yeast and its culture can stimulate specific microorganisms in the rumen, increase the number of anaerobic bacteria, especially fiber-decomposing bacteria, promote the growth of lactic acid-utilizing bacteria, increase beneficial microorganisms in the rumen, and maintain a constant environment in the rumen. In 2010, Sun Manji and other three feed yeast cultures independently selected and cultured by Northeast Agricultural University were used to feed the pre-lactating Holstein cows. The results showed that the addition of yeast culture significantly increased the total number of rumen bacteria, but had no significant effect on the number of rumen protozoa; yeast culture can significantly increase the total rumen volatile fatty acid, acetic acid, butyric acid and acetic acid, propionic acid ratio, However, there was no significant effect on the concentration of propionic acid; yeast culture significantly increased the relative viability of cellulase, which was beneficial to the degradation and utilization of cellulose in feed in the rumen. 5 Summary and outlook The difference in the effect of yeast cultures is partly due to differences in dietary characteristics, especially the level of rapidly fermented carbohydrates. When the concentration of non-structural carbon compounds (NSC) is less than 25% of the total dry matter in the diet, there is a lack of sufficient amount of metabolic energy to maintain the survival and fermentation of the yeast culture in the rumen. The effect of the yeast culture is not Significantly, it will even reduce milk production. In 2006, Wang Qiuju and others selected three Holstein cows with good fistula and good condition. The Latin square test design was used to study the effects of solid-fermented yeast culture and liquid deep-fermented yeast culture on rumen fermentation characteristics. The results showed that liquid fermentation had a better effect on the rumen fermentation characteristics than the solid fermentation yeast culture. There are many yeast culture products on the market, as well as reports on the application of yeast selenium, yeast chromium, yeast nucleic acid and compound yeast preparations in livestock and poultry production. Due to the differences in strains, activities, fermentation substrates, etc., the application effect It also varies widely. However, the effect of adding yeast cultures to dairy cow diets to improve rumen fermentation, stabilize the gastrointestinal environment, promote the growth of beneficial bacteria, and increase the milk yield of dairy cows is unquestionable. Therefore, yeast culture has a good application and promotion value in dairy cow production. Heilongjiang animal husbandry and veterinary Bathroom Mirror,Vanity Mirror With Lights,Bathroom Mirror With Lights,Bathroom Vanity Mirrors Duraplex Limited , https://www.duraplex.com.cn