In the past decade, the application of benzoic acid as an acidifier in pigs and poultry diets has been reported more and more.In this paper, the physicochemical properties, metabolic patterns in vivo, effects on pig and poultry production characteristics and mechanisms of benzoic acid were reviewed, and further studies were proposed in order to provide a more comprehensive and in-depth understanding of benzoic acid and its nutritional and physiological effects, and to provide more scientific basis for the scientific use of benzoic acid in production practice.
After Sweden banned antibiotics completely in the 1980s, other European countries followed suit until 2006, when the European Union banned the use of antibiotics in animal diets.In the process of searching for antibiotic substitutes, benzoic acid has been paid more attention by researchers because of its broad spectrum antibacterial effect and strong antibacterial power.In 2003, the European Union officially allowed the addition of 0.5%-1.0% benzoic acid in pig diets as an acidifier, and China's Feed Additive Varieties Catalogue (2013) regards it as an acidity regulator and preservative, allowing the use of 0.2-0.1g/kg in livestock and poultry diets.In recent ten years, more and more studies have been done on the application of benzoic acid as an antibacterial growth promoter.
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Physicochemical properties and bacteriostatic principle of benzoic acid
Benzoic acid, also known as benzoic acid, is the simplest aromatic acid whose carboxyl group is directly connected with the carbon atom of the benzene ring. Its acidity is weak, and the ionization constant is 4.20, which is longer than the medium chain
Fatty acid acid strong, with formaldehyde or benzene to stimulate the smell.Benzoic acid is slightly soluble in water, soluble in acetaldehyde, ethanol and other organic solvents;Not easily oxidized.The antiseptic mechanism of benzoic acid lies in its strong lipopilicity and easy to penetrate the cell membrane into the cell body, thus interfering with the permeability of bacteria and mold and other microbial cells, and inhibiting the absorption of amino acids by the cell membrane.The benzoic acid molecules entering the cell can ionize and acidify the alkali stored in the cell, and inhibit the activity of the respiratory enzyme system of the cell, prevent the condensation reaction of acetyl-CoA, and thus play A role in food preservation.Benzoic acid salts can be converted into the effective form of benzoic acid in acidic food and have the same antibacterial effect as benzoic acid.
The antiseptic mechanism of benzoic acid lies in its strong lipopilicity and easy to penetrate the cell membrane into the cell body, thus interfering with the permeability of bacteria and mold and other microbial cells, and inhibiting the absorption of amino acids by the cell membrane.The benzoic acid molecules entering the cell can ionize and acidify the alkali stored in the cell, and inhibit the activity of the respiratory enzyme system of the cell, prevent the condensation reaction of acetyl-CoA, and thus play A role in food preservation.Benzoic acid salts can be converted into the effective form of benzoic acid in acidic food and have the same antibacterial effect as benzoic acid.
The way benzoic acid is metabolized in animals
Bridges et al. used isotope C-labeled benzoic acid to study the way metabolites are excreted in the urine of humans and 20 species of animals fed benzoic acid.Studies have found that after benzoic acid enters the body, it is absorbed into the liver through the small intestine and excreted from the urine in four ways: one is catalyzed by enzymes to combine with glycine to form hemuric acid and excreted from the urine;The other is combined with glucuronic acid to form a formyl glucuronic acid, which is excreted from the kidney;It can also be excreted in the form of benzoic acid and uric acid.Some scholars believe that benzoic acid in urine is produced by the degradation of benzoyl glucuronic acid.
The most important metabolic pathway of most organic acids is that they are oxidized into carbon dioxide in the body and excreted through the lungs.Benzoic acid is mostly excreted in the form of equine uric acid and rarely enriched in the body. Therefore, the addition of benzoic acid in pig feed will not increase acid load and disturb the acid-base balance of the body.
Dietary supplementation of benzoic acid affects the growth performance of pigs and poultry, and the results of improving the growth performance of piglets are consistent, but the results of growing, finishing pigs and broilers are different.
Function of adding benzoic acid in feed
1, inhibit the growth of harmful bacteria and mold;Reducing the diarrhea of animals can replace the excessive addition of zinc oxide, which leads to the damage of animal digestive tract.It is beneficial to maintain the health of digestive tract.
2. Improve the reasonable structure of pig digestive tract;Make the smell of pig manure greatly reduced, reduce ammonia emissions, improve the livestock environment, conducive to respiratory health, conducive to environmental protection.
3. Lower urine pH value, change the environment of pig urethra, change the structure of parasitic microorganism population, maintain the health of pig urethra and reduce urinary system diseases.
4. Maintain the health of reproductive system of breeding pigs, reduce endometritis, mastitis and agalactia disorder syndrome of sows.
5. The addition of acidic substances can stimulate the secretion of digestive juices in animal intestines and improve the survival rate of piglets.
6. No drug, no risk of drug residue and drug resistance.
Effects of benzoic acid on digestive physiology of livestock and poultry
① Effects of benzoic acid on secretion and gene expression of glucagon-like peptid-2 (GLP-2) in intestinal mucosa of livestock and poultry.The intestinal morphology is related to the coefficient of nutrients and the barrier function. GLP-2 stimulates the proliferation and inhibits the apoptosis of cryopytes in intestinal mucosa, thus promoting the growth of intestinal mucosa and the regeneration and repair after injury.Increase intestinal blood supply, improve intestinal barrier function, promote intestinal absorption of nutrients and so on.The effect of benzoic acid on intestinal mucosal GLP-2 can be further analyzed to promote the improvement of intestinal morphology.
② Effects of benzoic acid on intestinal REDOX balance of livestock and poultry.Oxidative stress can lead to intestinal inflammation, damage intestinal function, affect the normal physiological functions of structural proteins and functional proteins in vivo, and then affect the growth and health of livestock and poultry.To study the effect of benzoic acid on intestinal antioxidant capacity can further analyze the mechanism of its protection of intestinal function and health.
③ Effects of benzoic acid on the endocrine and exocrine functions of porcine pancreas.After benzoic acid enters the animal body, the metabolic disease affects the endocrine function of the pancreas through the blood route, which provides a new direction for the study of the mechanism of benzoic acid improving the growth performance of pigs, and can further study the endogenous and exocrine mechanism of benzoic acid's effect on the nutrient digestion and metabolism of pigs.