With the improvement of living standards and the strengthening of health awareness, the problem of drug resistance and residue caused by feeding antibiotics has been paid more and more attention by the people. Developing antibiotic substitutes has become a hot topic in feed additives research. Sodium butyrate is one of the most widely studied antibiotic substitutes, which can promote animal growth, increase immunity, regulate intestinal microorganisms and other functions. Sodium butyrate is gradually being widely used in animal production.
Biological characteristics of sodium butyrate 1
Sodium butyrate is a short-chain volatile fatty acid-butyric acid with free and volatile characteristics, so it is made into relatively stable salt in animal husbandry and feed production. Sodium butyrate is decomposed into butyrate ion and sodium ion after entering animal body. Butyric acid is different from short-chain volatile fatty acids such as acetic acid or propionic acid. Butyric acid is diffusible in water and fat (water and fat parents). Butyric acid is more lipophilic. It is not easy to be decomposed in pH 4-6 environment. Butyric acid can avoid the intestine of water environment after feeding. Directly enter the cecum and colon continue to play a role.
Short-chain fatty acids include acetic acid, propionic acid and butyric acid. Butyric acid plays a major role in the hydrolysis of carbohydrates and proteins by anaerobic bacteria in the large intestine. Can: Regulate the absorption of sodium ions, induce epidermal cell proliferation, enhance mucosal blood flow, promote mucus secretion, etc., on the maintenance of cell differentiation and intestinal epithelial integrity plays an important role. In addition, butyrate can also play an effective bactericidal effect.
Nutritional and physiological functions of sodium butyrate 2
2.1 energy sources
As a preferred energy source of intestinal cells, SCFA is easily absorbed from the intestinal cavity. Butyric acid is the main energy source of colonic epithelial cells, and is consumed before propionic acid and acetic acid. Almost all butyric acid can be absorbed by intestinal epithelial cells. Therefore, butyrate is the main respiratory fuel of colon epithelium. Combining with the characteristics of non-ionic diffuse absorption of butyric acid, butyric acid can directly provide energy for intestinal epithelial cells without hepatobiliary absorption and complex trihydroxy circulatory system. It is a fast energy source for intestinal epithelial cells. Isotope tracing showed that butyric acid could enter the total blood circulation and almost all tissues could metabolize butyric acid.
2.2 maintain intestinal mucosal integrity.
The integrity of mucosal epithelial cells is a guarantee for their digestion and absorption. Wang Jifeng et al. (2005) added 1 g/kg sodium butyrate to the diet of piglets. The microstructure and ultrastructure of intestinal mucosal epithelium and goblet cells of piglets were studied by histology and scanning electron microscopy. The results showed that the mucosal epithelium of jejunum and colon was intact and the villi of intestine were thicker after sodium butyrate was added to diet; the mucosal absorption cells were high columnar, arranged neatly, and the free surface had obvious striated margin; the goblet cells were tall cup-shaped, scattered among columnar cells, and the number of cells was 1.4-1.7 times more than that of antibiotic group. Sodium butyrate can maintain the integrity of intestinal mucosal epithelial cells and promote intestinal digestion and absorption in weaned piglets, and is superior to antibiotics.
2.3 promote digestion and absorption
Many studies have shown that intestinal villus morphology is affected not only by livestock growth age and environment, but also by dietary composition and characteristics. A large number of studies have shown that sodium butyrate can effectively increase the intestinal villus height and reduce the depth of crypt, while the depth of shallow crypt and the height of long villus are the same. The best ratio to maintain gastrointestinal function.
Luo Haixiang (2006) showed that adding 0.1% sodium butyrate to the diet of weaned piglets significantly decreased the depth of duodenal recess (P < 0.05), decreased 42.12% compared with the control group, and had no significant effect on the villus height (P > 0.05), but the ratio of villus height to recess depth (VH / CD) was higher than the control group. 57.79% (P<0.05). It also significantly reduced the width of villi (P<0.05), which was 20.42% lower than that of the control group. The thickness of mucosa in the sodium butyrate group was 15.31 microns higher than that in the control group (P>0.05).
Hu et al. (2007) when adding sodium butyrate at different levels (500,1000,2000 mg/kg) to chicken diet, it was also found that sodium butyrate at 500 and 1000 mg/kg significantly increased the concentration of DNA, RNA and protein in duodenal mucosa (P < 0.05), and the ratio of villus height to crypt depth linearly increased with the increase of sodium butyrate (P < 0.05). .
2.4 enhance immune function.
The normal intestinal barrier is composed of mechanical barrier, chemical barrier, immune barrier and biological barrier. Mechanical barrier is the most important one in the intestinal mucosal barrier. Mechanical barrier refers to the intestinal mucosal epithelial structure which is closely connected with each other. It is composed of epithelial cells of intestinal mucosa, cell junctions on the side of epithelial cells, epithelial basement membrane and cell coat on the surface of epithelium. They form the first line of defense for the body's immune system. Therefore, the integrity of intestinal mucosal epithelial structure is closely related to the mechanical barrier function of intestinal mucosa, and even the immune function of the body. Wang Jifeng et al. (2005) showed that feeding 1 g/kg sodium butyrate to Weaned Piglets could promote the growth of goblet cells, maintain the normal morphology of intestinal mucosal epithelial cells, and maintain the normal mechanical barrier function of intestinal mucosa.
In addition, intestinal mucosal immune cells include lymphocytes, goblet cells, mast cells and so on, in which mast cells are natural