There are many kinds of additives for aquatic feeds, such as vitamins, minerals, binders, fungicides, colorants, attractants, etc. Vitamin C (Vc) is one of the vitamin additives. Since most aquatic animals are unable to synthesize Vc by themselves or have a small amount of synthesis that does not meet normal physiological needs, they must be continuously supplied by food. If the long-term intake is insufficient or underutilized, it will lead to animal material and energy metabolism disorders, resulting in lack of growth, developmental delay, disease resistance, anti-stress ability and even death. Therefore, in intensive farming, it is mostly supplemented in feed or added extra during the breeding process.
The use of Vc is now very common, but Vc is not resistant to high temperatures and is prone to deterioration during feed storage and loses its function, making Vc added types (dosage forms) and methods have their own particularities. Granular feeds, floating feeds and flakes in aquatic feeds are mostly subjected to high temperature and high pressure processes during the manufacturing process. Generally, Vc is often severely damaged, so the use of commercial protective Vc is necessary. of.
First, the dosage form of Vc
There are many types of Vc, which can be roughly divided into two dosage forms: ordinary Vc and protective Vc.
1. Ordinary Vc
Ordinary Vc is a general crystalline L-ascorbic acid. Because of its unstable molecular structure, it is difficult to store, it is easily damaged by light and heat, and its effectiveness is also very easy to decline. Therefore, the product is not directly used today.
2. Protected Vc Derivatives of ordinary Vc or a protective film on the outside of ordinary Vc.
(1) Derivatized Vc Derivatized Vc is a L-ascorbic acid hexacarbocyclic ring, and the structure on the second carbon is substituted with other chemical molecules to form a so-called derivative such as Vc polyphosphate, Vc phosphoric acid. Magnesium ester, Vc sulfate potassium, and the like. In addition to being used by cultured organisms, such derivatized Vc has the advantages of low dosage (about 1/5 to 1/10 of the use of L-ascorbic acid in grass shrimp) and good stability.
(2) The coating type Vc, also called the coating film Vc, is a processing technique that wraps the ordinary Vc or the derivatized Vc with a coating material such as a grease coating type Vc.
Most of the above two protective types of Vc are dosage forms used by feed factories in sinking and floating granular feeds.
Second, the use of Vc in feed processing and fish and shrimp farming process
1. Adding high-fat feed to Vc
Generally, high-fat feeds that are commercially available, such as squid floating feed, although Vc is additionally added, but the storage and transportation of the feed will reduce its utility, so additional addition is necessary. Vc is added to high-fat feeds and has two main functions. One is to reduce the production of free radicals, to avoid destroying vitamin E, and to regenerate it, as well as to protect feed fats and to avoid oxidative spoilage. Second, Vc itself is an antioxidant. One can avoid the production of methionine oxide in the feed, and the oxidation of the oil with lysine to improve the utilization of feed protein.
2. and shrimp use Vc
Fish and shrimp are in the fast growing season, so in terms of nutritional needs, high quality protein, fat, vitamins and other trace elements are needed to supply growth and development. In the vitamin part, the larvae lacking Vc are particularly prone to malformation. Vc is an important substance for synthesizing collagen in the vertebrae, especially fast-growing fish species such as sea otters and groupers. The addition of Vc is very prone to malformed individuals; while the general larvae are cultured in high-density and high-temperature environments, and physiological metabolism is particularly strong, so the demand for Vc is relatively higher than that of adult fish. In addition, the addition of Vc can assist in the synthesis of neurotransmitters, reducing the occurrence of larvae and shrimp convulsions.
3. Use of Vc when fish or shrimp are sick or injured
In the recovery process of sick and injured fish, the recommended amount of Vc is generally increased to 5 to 10 times. There are two main effects at this time: First, Vc can maintain the normal function of white blood cells, and regulate the proliferation of lymphocytes, accelerate the proliferation of lymphocytes, promote the increase of complement activity and enhance immunity; second, Vc as a part of the body iron An important substance for absorption and metabolism can promote hematopoiesis in organs such as bone marrow and spleen, and is beneficial to the formation of immune mechanisms.
4. and shrimp supplement Vc
The stocking of the species of shrimp is mostly high-quality protein and lipid, so adding Vc helps maintain the quality of the feed. In addition, the fish feed needs to be supplemented with Vc, VE and B groups. It is generally believed that Vc is accumulated in the adrenal cortex and is considered to be related to hormones. Therefore, in addition to stabilizing feed quality and enhancing immunity, Vc is added. It can also help the development of the gonads through the synergy of Vc and VE. In feeds (such as squid and grouper feed), if you have hormone-containing additives, you need to add Vc.
5. Use of fish and shrimp chronic copper ion poisoning
Copper ions play a lot of roles in the body. In shrimp, the main source of hemocyanin is involved in the function of carrying oxygen in the blood. In fish, it can catalyze the synthesis of red blood cells, promote the conversion of iron into transferrin, and it is incapable of hematopoiesis. Missing elements. In addition, copper ions are also important constituent elements of electron transport systems, connective tissues, bones, blood vessels and other tissues in fish and shrimp.
There are two main types of chronic copper ionosis in fish: heavy metals and drug poisoning; sources of chronic poisoning, mostly caused by the industrial sewage used in the culture ponds and the long-term use of copper sulfate drugs, while the latter are mostly. There are two main effects of chronic copper ionosis in fish: one is the accumulation of copper ions in the liver, which destroys the normal function of the liver, causing anemia symptoms; the second is the destruction of the respiratory epithelium, resulting in the loss of sputum function. It has been reported that Vc has an antagonistic effect on copper ions. Appropriate addition of Vc helps to enhance the absorption of copper ions in the intestine, thereby reducing the accumulation of copper ions in the liver. In addition, Vc also has detoxification functions for other heavy metals such as zinc, mercury, and arsenic.
Third, Vc deficiency
If the long-term intake of Vc and fish is insufficient or underutilized, it will lead to animal material and energy metabolism disorders, resulting in lack of growth, developmental delay, decreased resistance to disease and stress, and even death. The performance of Vc deficiency in different aquatic animals is different, but in general it can be summarized as spine curvature, cartilage deformation, collagen formation damage, skin and visceral hemorrhage, silkworm blackening, loss of appetite, slow growth, decreased fertility, and easy onset. , causing a large number of deaths.
Fourth, the recommended amount of Vc and its use notes
1. Adding method of Vc
There are roughly three ways to add Vc:
(1) Use of ordinary Vc: Most of the general Vc is mixed with drugs, vitamin E, highly unsaturated fatty acids or sterols, added to the powder or poured into the belly of the biological bait and then fed.
(2) Use of special Vc: Coated or derivatized Vc, except for the same as above, most of them are uniformly mixed with the powder, and then made into a bait or extruded and granulated. The amount of these two protective Vc additions is only 1/5 to 1/10 of the conventional (ordinary) Vc for livestock, but it must be adjusted with reference to the type of addition and its effective dose.
(3) Application to granular feed: Vc can be mixed with water or oil at the site, evenly sprayed on the granular feed, and then mixed with oil and fat after being dried in the shade. Or mix the water-soluble Vc with the oil and emulsifier and then spray it on the feed to feed the
2. Precautions for the use of Vc
The following five principles should be noted in the use of Vc:
(1) If the fish or shrimp after injury or recovery can still feed, the feed should be supplemented with at least 5-10 times of the usual amount to accelerate recovery.
(2) The amount of Vc added in different growth stages of different fish and shrimp will vary, and the amount of addition will decrease with age.
(3) It is also necessary to increase the amount of Vc added in high-density culture (such as intensive recirculating aquaculture of squid) or when the environment is stressed by cultured organisms.
(4) For different culture environments of cold, warm or high temperature, the amount of Vc added should be increased as the temperature increases.
(5) When selecting Vc of different dosage forms, it is necessary to consider the content of Vc (effective dose), the bioavailability of culture, and the loss rate during processing and feeding. At present, it is generally believed that the amount of Vc is normally required when the fish body grows normally and does not cause scurvy. The Vc dosage form is also an important factor affecting the normal demand, and the dosage of different dosage forms in the feed is also different.
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