The key role of various vitamins in aquaculture

Vitamins are necessary to maintain the health of aquatic animals and promote their growth and development. Many of these substances in the body cannot be synthesized by other substances or very few, and must be provided by food. If the intake is insufficient for a long time or can not meet the needs for other reasons, it will lead to metabolic disorders of fish and shrimp, growth retardation and decreased resistance to disease.

Vitamin classification

Vitamins can be divided into fat-soluble vitamins and water-soluble vitamins according to their solubility.

1. Fat-soluble vitamins: vitamin A, D, E, K, etc.

2. Water-soluble vitamins: vitamin B1, B2, B3, B5, B6, biotin (vitamin H, vitamin B7), folic acid, vitamin B12 and vitamin C, etc.

Fat soluble vitamins

1. Vitamin A: vitamin An is an unsaturated alcohol with β-Baizhi ketone ring. Vitamin An often forms esters with fatty acids in animals. Vitamin An is active and easy to be oxidized and destroyed by ultraviolet rays. The main functions of vitamin An are:

①, promote the synthesis of mucopolysaccharide, maintain the integrity of cell membrane and epithelial tissue and normal permeability.

②, which is involved in the formation of intracellular photosensitive substance (rhodopsin), plays an important role in maintaining the photosensitivity of the retina.

2. Vitamin D: vitamin D is a general term for anti-rickets substances, which belongs to sterol derivatives in chemical composition, of which D2 and D3 are the most common. D2, also known as ergot calcification sterol, D3, also known as bile calcification sterol, its molecular structure is very similar, only the side chain is different. Vitamin D is a colorless crystal with stable chemical properties and is not easy to be destroyed by acid, alkali, oxidant and heating. The physiological function of vitamin D is mainly to promote osteogenesis.

3. Vitamin E: vitamin E, also known as tocopherol, is stable to heat and acid, unstable to alkali and easy to be oxidized. It can protect vitamin An and unsaturated fatty acids from oxidation when it coexists with substances that are easy to be oxidized, such as vitamin An or unsaturated fatty acids. Therefore, vitamin E can be used as an antioxidant for these substances. The esters of vitamin E are stable and are often used as feed additives. The physiological function of vitamin E: anti-sterility function; as an antioxidant, it protects the unsaturated fatty acids on the cell membrane from oxidation, thus maintaining the integrity and normal function of the cell membrane; and protects the erythrocyte membrane to increase its resistance to hemolytic substances. At the same time, it can also protect sulfhydryl groups from oxidation and protect the activity of many enzymes. In addition, vitamin E also regulates tissue respiration and oxidative phosphorylation, and promotes the production of thyroid-stimulating hormone (TH), adrenocorticotropin (ACTH) and gonadotropin.

4. Vitamin K: vitamin K is a kind of quinone compounds, which is relatively stable and heat resistant, but it can be destroyed by alkali and light. The physiological function of vitamin K: participate in blood coagulation and promote liver synthesis of prothrombin and coagulation factors.

Water soluble vitamins

1, vitamin B1: also known as thiamine, is a white powder, its hydrochloride is acicular crystal, very soluble in water. B1 is stable in acidic solution, but easy to be destroyed by oxidation in alkaline and neutral solution. It is more abundant in yeast, cereal germ and cortex, lean meat, drupe and eggs. The physiological function of vitamin B1: as a coenzyme of pyruvate oxidative decarboxylase, α-ketoglutarate oxidative decarboxylase and transhydroxyacetaldehyde enzyme, vitamin B1 plays an important role in maintaining normal glucose metabolism in the body. In addition, B1 is also involved in the synthesis of valine in bacteria, yeasts and plants.

2. Vitamin B2: also known as riboflavin (it has this chemical name because its structure contains ribose and isoprazine, which is yellow). B2 is slightly soluble in water and alcohol, but insoluble in other organic solvents. It is stable in acidic solution, but it is easy to decompose in alkaline solution or exposure to visible light. B2 is widely distributed in animals and plants, such as rice bran, yeast, liver, milk and beans. The physiological function of vitamin B2: it exists in the form of Flavin mononucleotide (FMN) and Flavin adenine dinucleotide (FAD) in the body. FMN and FAD are coenzymes of many oxidoreductases in vivo, which play a role in hydrogen transfer in redox reactions. In addition, B2 plays an important role in maintaining the normal function of skin, mucosa and vision.

3, vitamin B3: also known as pantothenic acid, pantothenic acid, is a dipeptide derivative, can be soluble in water and ether. B3 is stable to oxidizer and reductant, and it is also stable when heating in the presence of water. But it is easy to be destroyed when heated in dry heat and acidic or alkaline medium. It widely exists in animals and plants, especially in wheat bran, rice bran and cruller. The physiological function of vitamin B3: it is the raw material for the synthesis of coenzyme An in vivo, and coenzyme An is a coenzyme related to acylation, which plays an important role in the transfer of acetyl group in the metabolism of sugar, fat and protein.

Vitamin B5 (nicotinic acid and nicotinamide): formerly known as vitamin PP or anti-leprosy vitamins, including nicotinic acid (niacin) and nicotinamide (nicotinamide). Both of them are white needle-like crystals and are stable for heat, light and acid. Nicotinic acid is slightly soluble in water, but largely soluble in alkaline solution, while nicotinamide is easily soluble in water and ethanol and heated in alkaline solution. Nicotinamide can be hydrolyzed into nicotinic acid. Nicotinic acid and nicotinamide are widely distributed in yeast, lean meat, liver, peanut, soybean, cereal cortex and germ. The physiological function of vitamin B5: nicotinic acid is not active until it is converted to nicotinamide in vivo. Nicotinamide is a component of coenzyme Ⅰ (NAD) and coenzyme Ⅱ (NADP), which plays an important role in redox reaction in vivo.

5. Vitamin B6: pyridoxine, which has three chemical forms, namely pyridoxine, pyridoxal and pyridoxamine. In vivo, pyridoxine can be converted to pyridoxamine and pyridoxal, but the latter two can not be converted to pyridoxine, while pyridoxal and pyridoxamine can change each other. Because pyridoxal and pyridoxamine are very unstable and are quickly destroyed by heat, light and air, B6 is generally supplemented in the form of pyridoxine hydrochloride. Pyridoxine hydrochloride is soluble in water and resistant to high heat in acid and alkali solutions, but it is easy to be destroyed when exposed to visible light. Vitamin B6 is widely distributed in nature, with high contents in grains, legumes, seed skins and Gramineae. The physiological function of vitamin B6: it is closely related to amino acid metabolism.

6. Biotin (vitamin H, vitamin B7): biotin is chemically stable and is not easily damaged by acid, alkali and light, but high temperature and oxidants can make it inactive. The physiological function of biotin (vitamin H, vitamin B7): it is a coenzyme of many carboxylase in the body, which participates in the carboxylation reaction in the process of material metabolism, such as the carboxylation of pyruvate to oxaloacetic acid and so on. It plays an important role in the synthesis of fatty acids in vivo.

Folic acid: folic acid, also known as anti-anemia factor, is yellow crystal, slightly soluble in water, stable in acidic solution, but easy to decompose when exposed to heat or light. The physiological function of folic acid: in vivo, folic acid is hydrogenated to tetrahydrofolic acid (THFA) by folate reductase. THFA is the coenzyme of body-carbon group transferase (such as-CH3,-CH2OH,-CH2-). The transfer of-carbon group is closely related to the synthesis of purine, pyrimidine and amino acid metabolism.

Vitamin B12: also known as cyanobalamin, it is pink crystal and is stable in weak acid solution, but it is easy to decompose when pH3 is below or above 9. B12 can be destroyed by the existence of oxidant and reducing agent. Animal liver and muscle contain more vitamin B12, but plants do not contain B12. Many microbes, such as some in the digestive tract of animals, can synthesize B12. The absorption of B12 depends on the presence of an internal factor in the intestine (mucin secreted by the intestinal wall). The physiological function of vitamin B12: participate in the metabolism of carbon groups in the body, is a coenzyme that transmits methyl, and its role is related to folic acid.

9. Vitamin C: also known as ascorbic acid, is a six-carbon polyhydroxylactone, with acidity and strong reducibility, soluble in water, stable in acidic solution, but quickly destroyed in alkaline solution. Because of its strong reducibility, it is easy to be destroyed by oxidants. The content of vitamin C is higher in green feed. The physiological functions of vitamin C:

Essential substances in the stroma such as ①, synthetic collagen and mucopolysaccharide

② can convert oxidized glutathione into reduced glutathione, thus protecting the active SH group of the enzyme and relieving the toxicity of heavy metals.

③, as a reducing agent, participates in the redox reaction in vivo.

④, involved in other metabolic reactions in the body, such as the conversion of folic acid to tetrahydrofolic acid, tyrosine metabolism and adrenocortical hormone synthesis.

⑤, intestinal absorption of iron also need vitamin C.

Choline: choline is a component of lecithin, which participates in the formation of lipoprotein and is conducive to the transport of fat from the liver, so it can prevent fatty liver. Choline has three unstable methyl groups and acts as a methyl donor in the transmethylation reaction. The physiological function of choline: acetylcholine, a derivative of choline, is important in the transmission of nerve impulses.

11. Inositol: inositol is a cyclohexane derivative, which is similar to choline and has obvious lipophilic properties. The physiological function of inositol: participate in the metabolism of some lipids to prevent fat deposition in the liver.

Vitamin K: a class of quinone compounds that are relatively stable and heat resistant, but can be destroyed by alkali and light. The physiological function of vitamin K: participate in blood coagulation and promote liver synthesis of prothrombin and coagulation factors.