Application of trace elements in aquatic animal feed
Trace elements are essential components of aquatic animals, especially iron, copper, zinc, manganese, diamond, iodine, selenium, chromium, etc., which are necessary for maintaining the normal internal environment of aquatic animals, maintaining the normal metabolism of substances, and promoting growth. Nutrients. Studying the nutritional, physiological effects and requirements of trace elements in aquatic animals has a positive effect on improving feed nutrients, improving feed efficiency, promoting aquatic animal growth and development, and maintaining health. Therefore, trace elements are increasingly causing aquatic animal nutritionists and The importance of farmers. In this paper, the research on the functional role of trace elements, the requirements of trace elements in aquatic animals and the addition of trace elements to feeds are summarized as follows:
First, the function and demand of trace elements
1. Iron
Iron is a component of heme and myoglobin and acts as a carrier for oxygen to ensure proper delivery of oxygen within the tissue. Iron is also a component of cytochrome enzymes and various oxidases, and is closely related to the process of cellular biooxidation.
The iron combined with inorganic iron and protein in the feed must be reduced to Fe2+ in the stomach or intestine and then absorbed. The presence of reducing substances in the feed can enhance the absorption of iron, and the absorbed Fe2+ is oxidized into Fe3+ in the intestinal mucosa cells. Combines with desferrin to form ferritin. The absorption of iron is restricted by ferritin present in intestinal mucosal cells, absorbing only the amount of iron required by the organism.
Increasing the iron content can cause an increase in the number of red blood cells of the arrowfish and the crescent, and anemia can occur when iron is lost in the feed. The results of blood and tissue testing for anemia caused by iron deficiency in squid, scorpion, river otter and river otter indicate that the addition of iron to fish feed is necessary. However, iron deficiency in feed does not affect the growth of fish and shrimp. Excess iron can cause iron poisoning. The iron content of 6mg/kg in the feed will inhibit the growth of shrimp. The content of iron in the feed is about 373mg/kg, which can maintain the normal growth of the gums, improve the defense ability, and prevent the adverse effects of other components in the feed on iron absorption and utilization. The requirements for iron in the Atlantic cockroach, cockroach, cockroach and channel catfish are between 30 and 170 mg/kg, and the amount required varies with the salt content. It is necessary to add 150mg/kg of ferrous chloride, and 200mg/kg when adding ferric citrate; 150mg/kg when squid is added to ferric citrate, and 170mg/ of ferric citrate as iron source. Kg of iron. The utilization of ferrous chloride and ferric chloride is higher than that of ferric citrate.
2, copper
Copper can participate in the absorption and metabolism of iron, which is necessary for hemoglobin and red blood cell maturation; it acts as an oxygen carrier of blood in mollusks and arthropods to participate in the transport of oxygen; it has effects on surface pigmentation, skeletal development, and reproductive and nervous systems. Features.
Although the demand for copper in fish is small (the average requirement for copper for feed for farmed fish is about 1-4 mg/kg), but because of its great effect, copper deficiency can lead to slow growth and cataract. The activity of cytochrome c oxidase, superoxide dismutase and ceruloplasmin in the heart of the river is reduced when copper is deficient. When the Chinese shrimp has a body length of 3.0 to 4.0 cm, the optimum copper content in the bait is 25.27 mg/kg, and when the body length is 6.0 to 8.0 cm, the copper content in the feed is preferably 53 mg/kg and 67 mg/kg. The cytochrome oxidase activity in the viscera is the highest and the growth is also the best. It indicates that the content of copper in the feed of Chinese shrimp is different at each stage of the growth process. Japanese prawns need copper content of 60mg/kg. Feeding of carp and juvenile fish with 0.7mg/kg copper slowed down; adding copper to 3mg/kg accelerated its growth. The demand for copper in rainbow trout is lower than that of squid, and its requirement should be higher than 0.7 mg/kg. In addition, tilapia requires 3 to 4 mg/kg of feed copper and 5 mg/kg of strontium. When the content of copper in the feed is too high (773 mg/kg or more), the growth is decreased and the feed efficiency is low. The amount of copper in the practical feed of juvenile larvae is about 5.6 mg/kg. The requirement for the feed copper of the channel catfish is 1.5 mg/kg, and the minimum requirement for copper is 5.1 mg/kg.
3, zinc
Zinc is distributed in all tissues of aquatic animals, with high levels of muscle and liver, is a component of many enzymes, and is an activator of certain enzymes such as alkaline phosphatase; it is also an essential component of insulin and its function. Participate in the structure of nuclear proteins and the metabolism of prostaglandins. Zinc is involved in the formation of melanin in larvae. Zinc deficiency in feed is slow or stagnant, loss of appetite, increased mortality, decreased levels of zinc and alkaline phosphatase in the serum, decreased levels of zinc and calcium in the bones, ulceration of the skin and fins, and cataracts in the rainbow trout. The lack of zinc causes metabolic disorders in nucleic acids and proteins, and the digestibility of proteins is also reduced. Zinc deficiency in the feed during the incubation period reduces egg yield and egg hatching rate. Zinc is an inorganic element essential for the growth of carp. It is severely deficient in zinc (the bait contains less than 1 mg/kg of zinc), causing death and rot of skin and fins. When the zinc content in the bait is 3mg/kg, the growth is slow, but the zinc can be taken from the environmental water. When the zinc content in the bait is 10～100mg/kg, the carp in the fish in the same water can consume more zinc than other fish. . Although rainbow trout and squid can tolerate 1700 to 1900 mg/kg of feed zinc, the optimum amount is 15 to 30 mg/kg. The optimum amount of zinc for channel catfish is 20 mg/kg. The grass carp had the best growth when the zinc content in the feed was 40-120 mg/kg. When the zinc content in the feed was below 20 mg/kg or above 160 mg/kg, the fish body was thin and poorly grown. The minimum requirement for zinc in feed for the channel catfish that live in soft water and hard water is 20-40 mg/kg, respectively. If the marine fish is used as the protein source, the zinc content in the Atlantic salmon feed should be greater than 67 mg/kg. In the semi-intensive system, it is not necessary to add trace elements to the Nile tilapia feed. Under laboratory and intensive conditions, a certain amount of zinc must be added to the feed. No zinc is added to the shrimp feed. The suitable content of zinc in rainbow trout and carp feed is 15-30 mg/kg, and channel catfish and blue tilapia are 20 mg/kg. However, in practical feed, 150 mg/kg zinc is needed to overcome the binding of phytic acid. . The content of zinc in the practical feed of gingiva should be above 119.2 mg/kg. The amount of zinc required for general aquaculture animals is 30-100 mg/kg.
4, manganese
Manganese is distributed in all tissues of aquatic objects with the highest content in bones. Manganese is mainly concentrated in mitochondria and is an activator of many enzymes; it is also a component of arginine, pyruvate decarboxylase and superoxide dismutase, and plays an important role in the tricarboxylic acid cycle.
If the manganese content in the feed is insufficient, the growth is poor, the tail of the rainbow trout is shortened, and the enzyme activity is decreased. The requirement for manganese in rainbow trout is 12-13 mg/kg. When the feed contains 2.4mg/kg of manganese, it can meet the needs of the channel catfish. Low-manganese broodstock with high mortality and low hatching rate. The utilization rate of manganese in fish meal is very high, and it is not affected by the content of tricalcium phosphate. However, manganese in fish meal can not meet the nutritional needs of carp. Adding 13mg/kg of manganese to carp feed can improve Growth rate to prevent bone formation from being blocked. The optimum requirement for grass carp for manganese is 15 mg/kg feed. In the semi-intensive system, tilapia feed does not have to be added separately due to sufficient manganese obtained from natural foods and water. Shrimp does not require manganese, and 3 mg/kg of manganese in the feed inhibits the growth of the shrimp. The requirement for manganese in feed for general cultured fish is 13 mg/kg.
5, drilling
Cobalt is involved in the formation of VB12, which has the function of preventing anemia; it is also an activator of certain enzymes. The addition of cobalt to the feed promotes the growth of the carp and the formation of heme. If cobalt is absent, the production of VB12 in the intestine will be severely reduced. Cobalt has a small ability to accumulate in fish. Excess cobalt is quickly expelled, and the distance between nutrient requirements and harmful amounts of cobalt is quite large. Cobalt poisoning is extremely unlikely to occur under actual feeding conditions. However, 0.1 to 5 mg/kg of cobalt in the feed is toxic to rainbow trout, resulting in gastrointestinal bleeding and leukocyte changes. The demand for cobalt in feed is 0.05 mg/kg, but the demand for cobalt in the feed may be higher than that of the gum. Prawns grew fastest when 0.05 to 0.075 mg/kg of cobalt was added to the feed.
6, iodine
Iodine is widely distributed in various tissues and organs, and more than half of it is concentrated in the thyroid gland, which is a component of thyroglobulin. Thyroid hormone can promote the growth and development of tissues and organs in the body. Iodine in the feed can prevent the occurrence of goiter. In the aquarium, the carp is cultured with water containing low concentration of iodine. As a result, the growth rate of the carp is lowered, and the iodine concentration is increased to 18 mg/L, which ensures the fastest growth of the carp. It is also found that increasing the iodine content can accelerate the growth of the goldfish. The amounts of iodine required for weights of 0.4 to 0.8 g and 8.5 to 50 g were 0.6 μg/kg and 1.1 μg/kg, respectively. The requirement for iodine of 5-6 cm shrimp is 30 μg/kg. The required amount of iodine for aquaculture animals is generally 0.03 to 0.1 μg/kg.
7, selenium
Selenium is a toxic element, but it is also an essential element of life activities. It can prevent the oxidation of lipids in cell mitochondria, protect cell membrane from damage by lipid metabolism by-products, be a cofactor for glucose metabolism, and protect against the toxic effects of certain metals. Lack of selenium can lead to increased mortality. The lack of both selenium and VE causes muscle malnutrition and degeneration. Adding 0.44mg/kg of selenium to the feed is beneficial to the growth of Chinese shrimp. Deficiency of selenium in salmonids can lead to muscle malnutrition, anemia and even death. The requirement for selenium in rainbow trout is between 0.15 and 0.38 mg/kg. Large scale salmon can maintain a normal growth rate when the selenium content is below 0.25 mg/kg. Under the premise of sufficient supply of VE, the required amount of channel catfish selenium with a weight of 70-90 g is 0.25 mg/kg. The minimum amount of selenium required is largely dependent on the VE in the feed, which is generally 0.2 to 0.5 mg/kg.
8, chrome
Chromium exists in the feed in the form of inorganic Cr3+ and a portion of the biologically active molecule. Trivalent chromium contributes to the normal metabolism of lipids and sugars and maintains a constant cholesterol in the blood. Its biological function is related to insulin. The addition of 0.5 mg/kg of chromium to the feed does not cause the meat quality change and toxicity of the squid, does not cause toxicity to the fish, promotes the growth of fish and increases the effect of feed conversion.
Second, the interaction between trace elements
Studies have shown that there is a clear synergy between iron, copper and cobalt. Iron is one of the raw materials for the formation of hemoglobin. Copper and cobalt promote the growth and maturation of red blood cells. The lack of any of these three trace elements in the feed can cause red blood cell disorders. It is known that manganese has synergistic effects with iron, cobalt, zinc, iodine and cobalt; and zinc has an antagonistic effect with chromium, iron, selenium and copper.
Third, trace element feed additives
The most common compound for iron in feed is ferrous sulfate, but it has certain drawbacks, such as strong moisture absorption, easy oxidation, antagonism with many nutrients, and other traces of physicochemical properties that are unstable during digestion and absorption. The bioavailability of elemental compounds is reduced. And ferrous sulfate can not meet the nutritional requirements of all aspects of immortal animals, and is gradually replaced by ferrous citrate. Copper sulfate has a good bioavailability, but it is easy to absorb moisture and is difficult to process. Copper oxide has poor bioactivity and water solubility, but it has less damage to other nutrients in the feed. Copper oxide is generally used as a copper source in foreign countries. Zinc sulfate has high biological activity and is often used as a source of zinc in feed. The additive for manganese in feed is mainly manganese sulfate. Most of the iodine feed additives are potassium iodate. Sodium selenate or sodium selenite is used as a selenium feed additive due to its high bioavailability.
Inorganic salt trace element additives are easy to oxidize, have low absorption rate and poor nutrition. The research of trace element additives has been developed from inorganic salts to amino acid chelate salts. The amino acid chelate salt is a chelate compound of an amino acid and a trace element, and is an additive of a nutrient-type feed trace element having a high biological titer, and is an updated product of an inorganic salt and an organic salt additive. The amino acid chelate salt is integrated into a variety of amino acids and trace elements, and has the advantages of comprehensive nutrition, high absorption rate, good chemical stability, obvious growth promoting effect, sterilization and improvement of immune function, and can greatly reduce the cost of breeding, and overcomes the advantages. The shortcomings of inorganic salt trace element additives have become the third generation of new trace element additives that have developed rapidly at home and abroad.
The absorption rate of trace elements after amino acid sequestration in aquatic animals is 1.25 to 2.5 times that of inorganic salts, which has greater and superior general absorption and digestion and metabolism than inorganic salt trace elements. With the addition of amino acid chelate salt additive, the average specific growth rate of tilapia increased by 79.61%-89.25% compared with the inorganic salt control group; the average specific growth rate of the carp chelated salt test group was 55% higher than that of the control group; The average specific growth rate of the salt test group was 36.45%-64.49% higher than that of the control group, and the content of trace elements in liver, muscle and blood was higher than that of the inorganic salt group. Similar results were obtained in squid, tilapia, Chinese prawn, Atlantic salmon, and bigmouth bass. In general, the absorption rate of amino acid chelated copper is 1.5 times larger than that of carbonate, 2.25 times larger than sulfate, and 1.25 times larger than oxide; the absorption rate of amino acid chelated magnesium is 1.8 times larger than that of carbonate. 2.5 times larger; the absorption rate of amino acid chelated iron is 1.5 times larger than that of carbonate, 1.8 times larger than sulfate and 2.5 times larger than oxide; amino chelated zinc is 2.1 times larger than sulfate and 2.5 times larger than oxide. .
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