Citric acid is formed by carboxylation of acetyl-CoA and oxaloacetate in the body's tricarboxylic acid cycle, and participates in the metabolism of sugar, fat and protein in the body. Natural citric acid exists in the bones, muscles, and blood of plants (such as lemons, citrus and pineapples) and animals, and artificially synthesized by fermentation of sugar-containing substances such as sugar, molasses, starch, and grapes. Adding citric acid to compound feed can disinfect, prevent mildew, and prevent salmonella and other infection of animal feed. The intake of citric acid by animals can reduce the proliferation of pathogens and inhibit the production of toxic metabolites, and improve the stress ability of animals.
Adding citric acid to the diet can improve the palatability of the diet. Citric acid can directly stimulate the taste bud cells in the mouth, increase the secretion of saliva, play the role of a flavoring agent, enhance the appetite of animals, and thus increase the feed intake of animals. Adding citric acid to the diet can reduce the pH of the diet. After the animals eat, the acidity in the stomach decreases, and the inactive pepsinogen is converted into active pepsin, or directly stimulates the secretion of digestive enzymes; in addition, after acidic chyme entering the small intestine, it stimulates the small intestine to secrete enterostatin, which reflexively inhibits gastric peristalsis, delays gastric emptying, increases the time for chyme to pass through the intestine, and promotes the digestion of nutrients.
Organic acids can enter the cell wall of bacteria, causing pH gradient changes inside and outside the bacteria, inhibiting bacterial growth. The suitable pH for the growth of several common pathogens is neutral and alkaline. For example, the suitable pH of Escherichia coli is 6.0-8.0, that of Streptococcus is 6.0-7.5, and probiotics such as lactic acid bacteria are suitable for breeding in acidic environment. Citric acid reduces the pH in the gastrointestinal tract, and probiotics such as lactic acid bacteria in the intestinal tract get good growth conditions, thereby maintaining the normal balance of microbial flora in the digestive tract of livestock and poultry.
Immunocompetent cells, namely T lymphocytes and B lymphocytes, play an immune surveillance role in the body. Studies have shown that feeding broilers with citric acid can make the immune cells have a higher density, so that the chickens are in a better immune state, which can inhibit the reproduction of intestinal pathogens and prevent the occurrence of infectious diseases.
Citric acid is a natural preservative. Since citric acid can reduce the pH of the feed, the proliferation of harmful microorganisms and the production of toxins are inhibited, and it has an obvious anti-fungal effect. As a synergist of antioxidants, the mixed use of citric acid and antioxidants can improve the antioxidant effect, prevent or delay the oxidation of feed, improve the stability of compound feed and prolong the storage period.