Application of Yeast Feed Additives in Pig Industry
Yeast (Saccharomyces cerevisiae) is a unicellular microorganism belonging to fungi, with strong acid resistance. Yeast cells are rich in protein, amino acids, nucleic acids, vitamins, digestive enzymes, and trace elements such as selenium, chromium, iron, and zinc, and the protein content accounts for 30% to 50% of the dry weight of the cells.
Yeast cell walls contain a variety of biologically active substances,35% to 60% are zymosan, namely mannose oligosaccharide and β-glucan. Yeast is widely distributed, and its growth has the characteristics of prokaryotic reproduction and can multiply rapidly. Yeast feed additives can effectively improve the balance of flora in the digestive tract of livestock and poultry, enhance immunity, and provide rich nutrients, so as to achieve multiple functions such as prevention and treatment of digestive tract diseases and promoting growth. It is a green feed additive with characteristics such as drug resistance.
Yeast feed additives are widely used in animal husbandry, and are usually divided into feed yeast, wall-breaking yeast powder, yeast shell, active dry yeast, yeast culture, enriched trace element yeast and yeast as a carrier to express excellent foreign genes. Biosynthetic products. The application of yeast feed additives in the pig industry is mainly in the following five aspects:
The direct nutritional effect
Yeast cell protein accounts for about 32% to 75% of the dry matter of the cell body. It has been reported that the protein contained in every 100kg of dry yeast is equivalent to the protein content of 500kg of rice, 217kg of soybeans or 250kg of pork. And its lysine and tryptophan content are high, the former content is close to animal protein, adding yeast to the feed can make up for the lack of lysine in grains. And feeding yeast is much less expensive than feeding soy and fishmeal.
Yeast is rich in nucleic acids, vitamins and trace elements. Yeast cells contain 4.5% to 8.5% ribonucleic acid, about 2% B vitamins and various minerals. Minerals account for about 3% to 10% of the dry weight of yeast cells, with the highest phosphorus content, followed by potassium, calcium, sulfur, and sodium. Wait. In addition, some yeasts also have the function of enriching trace elements, making them from inorganic to organic, which is conducive to the absorption and utilization of animal bodies. Yeast copper, yeast iron, yeast manganese and yeast selenium have been included in the catalogue of feed additives in my country.
In foreign countries, the general amount of yeast added in pig diets is 2% to 5%. In some cases, dry yeast powder can even be used to replace 80% of animal protein without adverse effects on weight gain and production performance. Experiments have shown that feeding live yeast cultures to weanling pigs can increase their feed intake and daily gain without altering their gut microbiota and fermentation products. When applying yeast in pig production, it should be noted that high-energy and low-protein feed should be used together with yeast; lactating sows should not be fed fresh yeast to avoid diarrhea in piglets.
2. Improve the gastrointestinal environment and promote the digestion and absorption of nutrients
Active dry yeast, wall-breaking yeast powder and yeast culture can be used as microecological preparations to improve the ecological environment of animal gastrointestinal tract. Yeasts are facultative anaerobic bacteria, which grow and reproduce in animals. They can consume oxygen in the intestinal tract to create an anaerobic environment, and metabolize to produce organic acids such as lactic acid, which is conducive to the growth of intestinal beneficial bacteria such as lactic acid bacteria and inhibits E. Therefore, it can improve the gastrointestinal environment and flora structure, and promote the digestion, absorption and utilization of nutrients by the gastrointestinal tract. The mannan (MOS) contained in the wall-breaking yeast powder can selectively adsorb various mycotoxins and prevent the colonization and proliferation of pathogenic bacteria, improve the flora structure of the animal digestive tract, and also play a role in maintaining the microecological balance of the animal intestinal tract.
Yeast itself is rich in enzymes, such as monopepsin, amylase, cellulase and phytase. These enzymes can hydrolyze starch and cellulose into low-molecular-weight substances that are easily digested and absorbed, such as small-molecule sugars, amino acids, and alcohols.
Lei Hongjun et al. (2006) used S. boula to feed pregnant and lactating sows, which reduced the weight loss of sows at weaning, significantly reduced the mortality of weaned piglets, and increased the feed intake of lactating sows. The study by Wang Xuedong et al. (2006) showed that the average daily gain of piglets before weaning at 21 days of age was significantly higher than that of other groups when the active dry yeast was added in the diet of 1 × 106 and 2 × 107 CFU/g group. Appropriate amount of active dry yeast can increase the feed intake of lactating sows, the weaning rate of piglets and improve the structure of sows' gastric flora.
3. Improve the body's immunity
Yeast trace elements, zymosan, functional polypeptides, nucleotides, etc. all have the effect of improving the immune level of animals. The yeast cell wall accounts for about 20% of the weight of yeast, and the main components are functional polysaccharides such as β-glucan (57%) on the inner wall and mannose oligosaccharide (6.6%) on the outer wall. β-glucan can stimulate the production of animal body. Macrophages, which play a key role in immune function, remove damaged, dying cells and pathogenic microorganisms that invade the body. Mannan oligosaccharide improves immunity by increasing the level of immunoglobulin and improving the activity of macrophages.
The immune system of weaned piglets is relatively weak, and the use of zymosan can rapidly enhance active immune function, reduce weaning stress, and improve piglet survival rate. Jurgens et al. (1997) applied Saccharomyces cerevisiae to corn-soybean meal type diet to feed piglets, which can improve piglet daily weight gain and feed remuneration; feeding pregnant sows and lactating sows can increase sow milk concentration. γ-globulin content.
Yeast selenium and yeast chromium increase immunoglobulin levels and reduce morbidity. In recent years, studies have found that selenium plays an important role in the effective operation of the animal immune system. Organic selenium can enhance the body's cellular immune function, enhance the ability of lymphocyte transformation and delayed type hypersensitivity (DTH), and organic selenium can enhance humoral immunity and stimulate immunity. globulin formation. The results of Zhong Chonghua et al. (2006) showed that adding 0.3 mg/kg yeast selenium to the diet of weaned piglets can significantly increase the serum IgA concentration and the T lymphocyte transformation rate. Heugten et al. (2003) showed that the addition of 0.2 mg/kg organic chromium to the diet of weaned piglets under stress conditions can improve humoral immune function.
4. Improve animal growth performance and reproductive capacity
Trace mineral elements such as selenium, chromium and zinc are of great significance to the growth of animals, and can be divided into two categories: inorganic and organic. Elemental yeast is one such organic form. Yeast trace elements have the characteristics of high binding rate, strong biological activity, high utilization rate and good safety. Eleanor et al. (2006) reported that adding 0.3 mg/kg yeast selenium to the diet of pregnant sows could significantly increase the average embryo weight, length and embryo protein and DNA content compared with inorganic selenium; improve embryo selenium levels, And reduce piglet VE content. Bobcek et al. added 0.3 mg/kg yeast selenium to the growing-finishing pig diet, and the results showed that compared with inorganic selenium, yeast selenium could increase pork pH, improve meat color, reduce muscle conductivity and drip loss. Zhao Jinxiang (2009) research shows that adding yeast zinc to feed can increase the average daily feed intake of weaned piglets and reduce the feed to meat ratio. Adding 200 mg/kg yeast zinc to the diet can achieve 2000 mg/kg zinc chloride. The growth-promoting effect of yeast zinc group was much lower than that of zinc chloride group.
Mineral elements such as chromium and selenium are of great significance to reproductive performance. Selenium has specific effects on sperm formation and development. Selenium is one of the components of sperm mitochondrial outer membrane selenoproteins, which can protect sperm cell membranes from damage; selenium deficiency can damage the physiological function of uterine smooth muscle, resulting in retained placenta and reduced fertilization rate. Organic selenium also improves sow reproductive performance and reduces stillbirth rates. Chromium can increase sow ovulation, thereby improving sow reproductive performance. Mahan et al. (2004) and Yoon et al. (2006) showed that adding 0.3 mg/kg organic selenium to the diet of pregnant sows could reduce litter mortality; adding 0.15 mg/kg organic selenium could increase the litter size Total live births. Tan Bin et al. (2008) showed that adding active dry yeast products to the feed of piglets and pregnant sows can significantly improve the growth rate of weaned piglets, the reproductive performance of sows, and reduce the incidence of constipation in sows.
5. Application of Environmental Protection Breeding
Modification of mannan will further improve its ability to bind mycotoxins such as aflatoxin and zeatin. Therefore, mannan in yeast cell wall is called a new type of adsorbent. Zymosan has a strong decomposition effect on the deposition of toxins in animals caused by feed mildew and other reasons, and can effectively reduce the odor of animal excrement, thereby reducing the reproduction of flies and maggots, reducing ammonia in the house, and improving the environment in the house.
Probiotics such as live yeasts are not only widely used in feed and drinking water, but also sprayed into livestock houses. In recent years, the cultivation mode of fermentation beds has been relatively successful. The main principle is to rely on the ability of microorganisms to decompose and transform. As one of the many species of fermentation beds, live yeasts work synergistically with other non-fungal microorganisms to complete substances in the cultivation ecosystem. conversion of energy.
In the pig industry,yeast additives have been widely used and played an important role. It can improve animal production performance and economic benefits, and is conducive to obtaining high-quality livestock products; at the same time, it can improve animal health and can be used as an effective substitute for antibiotic additives; to a certain extent, it can reduce pollution and play a role in environmental protection.