What are the effects of beer yeast on the gut microbiota of livestock

      Feed grade beer yeast has a significant regulatory effect on the gut microbiota of livestock, poultry, and aquatic animals. Its core mechanism is to change the composition, quantity, and metabolic balance of gut microbiota through the nutritional components (such as proteins and amino acids), active substances (such as β - glucan, mannan, organic acids), and metabolic products (such as short chain fatty acids) of yeast cells themselves, ultimately achieving the effect of "promoting beneficial bacteria and inhibiting pathogenic bacteria". The following elaborates on the impact of livestock and aquatic animals on gut microbiota:

1、 The impact on the gut microbiota of livestock and poultry

      The gut microbiota of livestock and poultry (such as pigs, chickens, cows, etc.) is mainly composed of bacteria (such as lactic acid bacteria, Escherichia coli, bifidobacteria, clostridia, etc.), while beer yeast mainly regulates the balance of the microbiota through "competitive exclusion", "nutrient supply", "environmental regulation" and other methods:

1. Inhibit the proliferation of harmful bacteria and reduce the risk of intestinal infections

      Targeted inhibition of pathogenic bacteria adhesion and colonization: Mannan (MOS) in the cell wall of beer yeast can bind to "adhesion factors" on the surface of pathogenic bacteria such as Escherichia coli, Salmonella, and Clostridium perfringens (similar to "competitive occupation"), preventing these pathogenic bacteria from adhering to intestinal mucosal cells, preventing them from colonizing and being excreted with feces. For example:

      After adding 2% beer yeast to the diet of piglets, the number of Escherichia coli in the intestine decreased by 40% to 60%, and the detection rate of Salmonella decreased from 30% to below 10%, effectively reducing the incidence of yellow and white dysentery (caused by Escherichia coli) in piglets.

     Adding beer yeast to broiler feed can reduce the number of Clostridium perfringens (the main pathogenic bacteria causing necrotizing enteritis) in the intestine by 50% to 70%, and the content of toxins (such as alpha toxins) produced by them is reduced, resulting in a significant decrease in the incidence of intestinal inflammation.

      Lowering intestinal pH and inhibiting neutral/alkaline pathogenic bacteria: After being partially decomposed in the intestine, beer yeast can produce small amounts of organic acids (such as lactic acid and acetic acid), while promoting the proliferation of beneficial bacteria (such as lactic acid bacteria) and secreting more short chain fatty acids (SCFAs), reducing intestinal pH from 6.5~7.0 to 5.5~6.0. This acidic environment has a direct inhibitory effect on the growth of neutral/alkaline pathogenic bacteria such as Escherichia coli and Salmonella (with an optimal pH of 7.0-7.5), but has no effect on lactic acid bacteria (with an optimal pH of 5.5-6.5).

2. Promote the growth of beneficial bacteria and optimize the structure of the microbial community

      Providing nutrient substrates for beneficial bacteria: β - glucan and oligosaccharides in beer yeast are the "exclusive nutrient sources" for beneficial bacteria such as lactic acid bacteria and bifidobacteria, which can promote their rapid proliferation. For example:

      After adding beer yeast to weaned piglets, the number of lactic acid bacteria in the gut increased by 30% to 50%, the number of bifidobacteria increased by 20% to 40%, and the proportion of beneficial bacteria in the gut microbiota increased from 40% to over 60%.

      Adding beer yeast to the diet of laying hens significantly increased the number of lactic acid bacteria and bifidobacteria in the cecum, with the proportion of lactic acid bacteria increasing from 25% to 40%. These beneficial bacteria can further inhibit pathogenic bacteria by producing antibacterial substances such as bacteriocins.

      Improving the intestinal microenvironment and creating living conditions for beneficial bacteria: Vitamins (such as B vitamins) and amino acids (such as glutamine) produced by beer yeast metabolism can provide coenzymes and energy for beneficial bacteria to grow. At the same time, the adsorption of yeast cell walls can remove harmful metabolites such as ammonia and hydrogen sulfide in the intestine (which inhibit beneficial bacteria growth), indirectly promoting beneficial bacteria reproduction.

3. Maintain gut microbiota diversity and enhance microbiota stability

      A healthy gut microbiota requires a high level of diversity (diverse flora) to cope with external environmental changes (such as feed changes and stress). Beer yeast can maintain microbial diversity through the following methods:

      After weaning piglets, the gut microbiota is prone to "microbiota imbalance" due to stress (a sudden increase in pathogenic bacteria and a decrease in beneficial bacteria). Adding beer yeast can increase the number of OTUs (reflecting microbiota diversity) in the gut microbiota by 15% to 20%, and the microbiota structure is more stable, reducing the risk of diarrhea caused by stress.

      After adding beer yeast to the rumen of beef cattle, the proportion of functional bacteria such as fiber degrading bacteria (such as rumen cocci) and methane producing bacteria is more coordinated, and the diversity of the bacterial community is increased, which helps to improve the digestibility of crude fiber and reduce severe fluctuations in rumen pH (to avoid acidosis).

2、 The impact on gut microbiota of aquatic animals

      The intestinal environment of aquatic animals (such as fish and crustaceans) (such as low salt, high moisture, and large temperature fluctuations) is significantly different from that of livestock and poultry. Their intestinal microbiota is mainly composed of aquatic bacteria (such as Vibrio, lactic acid bacteria, and Bacillus), and the regulatory effect of beer yeast focuses more on "inhibiting aquatic pathogenic bacteria and promoting low oxygen tolerant beneficial bacteria":

1. Inhibit aquatic pathogenic bacteria and reduce infection rates

      Targeted inhibition of Vibrio: Vibrio (such as Vibrio parahaemolyticus and Vibrio harveyi) is the main pathogenic bacterium in aquatic animals (such as shrimp and sea bass), which can cause enteritis and sepsis. The mannan in beer yeast can bind to the "adhesion protein" on the surface of Vibrio, preventing it from adhering to the intestinal mucosa (adhesion is a prerequisite for infection), reducing the number of Vibrio in the intestine by 50% to 70%. For example:

      After adding 3% beer yeast to the feed of Vannamei shrimp, the detection rate of intestinal Vibrio decreased from 80% to 30%, and the mortality rate of "stealing death disease" (caused by Vibrio) decreased by 40% to 60%.

      Inhibition of fungi and parasites: Lysozyme analogs and organic acids produced by beer yeast metabolism can inhibit the reproduction of water mold (fish fungal disease) and intestinal parasites (such as ring worms), reducing their damage to intestinal mucosa.

2. Promote the proliferation of beneficial bacteria with low oxygen tolerance and optimize intestinal function

      Aquatic animal intestines are in a relatively low oxygen environment, and beneficial bacteria are mostly facultative anaerobic bacteria (such as lactic acid bacteria and Bacillus). Beer yeast can promote its growth through the following ways:

      Provide nutrition in anaerobic environments: Nucleotides and small molecule peptides in beer yeast can serve as energy sources for lactic acid bacteria in low oxygen environments, promoting their proliferation. For example:

      After adding beer yeast to the diet of grass carp, the number of lactic acid bacteria in the intestine increased by 30% to 40%, and the number of Bacillus increased by 20% to 30%. These bacteria can secrete proteases and amylases, improve feed digestibility, and produce antibacterial substances (such as lactic acid) to inhibit pathogenic bacteria.

      Improving intestinal redox environment: Glutathione (antioxidant substance) in beer yeast can reduce the accumulation of reactive oxygen species in the intestine, creating a more suitable living environment for facultative anaerobic bacteria (such as Bacillus), increasing their proportion in the intestinal microbiota from 20% to over 40%.

3. Regulate microbial metabolism and reduce the production of harmful substances

      Aquatic animals' gut microbiota metabolism is prone to produce harmful substances such as ammonia and nitrite (which can contaminate water quality and damage the gut). Beer yeast can reduce these substances by regulating microbial metabolism:

      Reduce ammonia nitrogen levels: Urease inhibitors in beer yeast can inhibit pathogenic bacteria (such as Escherichia coli) from producing urease (urease breaks down proteins to produce ammonia), while promoting beneficial bacteria (such as lactic acid bacteria) to convert ammonia into amino acids, reducing intestinal ammonia concentration by 30% to 50%. For example:

      Excessive ammonia content in the intestine of tilapia can cause damage to the intestinal mucosa. After adding beer yeast, the ammonia concentration decreased from 15 mg/L to below 8 mg/L, and the integrity of the intestinal mucosa was significantly improved.

      Increase the production of short chain fatty acids (SCFAs): Beer yeast, when decomposed by beneficial bacteria, can produce SCFAs such as acetic acid and propionic acid. These substances not only lower intestinal pH (inhibit pathogenic bacteria), but also provide energy for intestinal mucosal cells and promote intestinal development. For example:

      After adding beer yeast to crayfish, the intestinal SCFA content increased by 20% to 30%, the length of intestinal villi increased by 15% to 20%, the intestinal absorption area expanded, and the digestibility of feed protein increased by 10% to 15%.

4. Microbial balance adapted to high-density aquaculture

      In high-density aquaculture, there are many pathogens and high stress in the water, and the gut microbiota is prone to imbalance. Beer yeast can enhance the anti-interference ability of bacterial communities:

      The proportion of pathogenic bacteria (such as Pseudomonas) in the gut of high-density farmed sea bass can reach over 60%. After adding beer yeast, the proportion of beneficial bacteria (such as lactic acid bacteria) increases to over 50%, and the microbial community structure is more stable. Even if the concentration of pathogens in the water increases, the gut microbiota is not easily collapsed, and the survival rate increases by 20% to 30%.

Summary: Core Regulation Law

      The impact of beer yeast on the gut microbiota of livestock, poultry, and aquatic animals is common: it achieves gut microbiota balance by "inhibiting the adhesion and proliferation of pathogenic bacteria, promoting the growth of beneficial bacteria, and optimizing microbiota metabolism". The specific difference lies in:

      Livestock and poultry intestines: focus on inhibiting terrestrial pathogenic bacteria (such as Escherichia coli and Salmonella), promoting symbiotic bacteria such as lactobacilli and bifidobacteria, and enhancing intestinal digestion and immune barriers;

      Aquatic animal gut: focuses on inhibiting aquatic pathogenic bacteria (such as Vibrio), promoting low oxygen tolerant beneficial bacteria (such as Bacillus), while reducing harmful substances such as ammonia nitrogen to adapt to the characteristics of the water environment.

      This regulatory effect can reduce the use of antibiotics, improve animal growth performance and survival rate, and is an important means of improving intestinal health in green farming.