First, the necessary trace elements
Trace elements are extremely small elements in the body. The extent of the number and the discovery of physiological functions are closely related to the sensitivity development of the test methods. Early analytical techniques were unable to accurately determine the concentration of their presence. Therefore, an element that is required for an animal but is difficult to quantify is called a trace element. By the 1950s, the emergence of atomic absorption spectrophotometry greatly improved the precision of trace element determination methods, especially the quantitative research.
It has been found that almost all known chemical elements are present in living organisms, and some people believe that there are more than 60 elements in the living body.
Former Soviet scholars divided them into three categories based on their content in the body:
The content of 0.01% (100mg/kg) or more is called a large number of elements or constant elements (Majorelement, Macrocomponent);
An amount of 0.00001% ~ 0.01% (0.1mg / kg 100mg / kg) are known as trace elements or Traceelement): kSj
0.00001% (0.1 mg/kg) or less is called ultra-trace element (Ultraceelement).
Some scholars divide it into two categories, namely a large number of elements (in vivo content greater than 0.01%) and trace elements (in vivo content less than 0.01%) .
In fact, we are used to collectively refer to trace elements and ultra-microelements as trace elements. The classification of trace elements varies according to their standards. Some are classified according to the content of trace elements in the body, and some are classified according to the affinity of trace elements for animal organs and tissues. However, since this classification method cannot reflect the importance of trace elements to the living organism, the practical significance is not significant. Therefore, it is generally based on the biological role of the animal body, the trace elements are divided into three categories, that is, essential trace elements, possibly trace elements and unknown trace elements.
Essential trace elements have special functions for animals and are necessary for normal physiological and biochemical processes in animals. Currently, there are 16 kinds of essential trace elements , including iron, manganese, copper and zinc. The physiological functions of nine trace elements such as cobalt, molybdenum, iodine, fluorine and selenium are well understood. The knowledge of the remaining seven trace elements such as chromium, nickel, vanadium, tin, arsenic and antimony is less known. The elements are also known as the new seven essential trace elements.
Non-essential trace elements are harmless and harmful. The currently known non-essential trace elements mainly include more than 30 kinds of harmless elements such as aluminum (AI), barium (Ba) and bromine (Br), and six kinds of harmful substances such as bismuth (Bi), antimony (Sb) and cadmium (Cd). element.
Trace elements may be required between the necessary trace elements and non-essential trace elements. They have been found to have an effect on actual physiological and biochemical properties. However, its specific physiological functions have not yet been clarified and need further study.
In the field of essential trace elements, there is a big difference in the meaning of “essentialâ€. However, it is generally believed that essential trace elements mainly mean that animals cannot be synthesized, and can only rely on exogenous feed, water and other foods. Mineral elements, animals lacking this element can not survive, production can be characterized by slow growth, decreased production and reproductive performance and reduced economic benefits . The classification of trace elements is limited to the current level of understanding of these elements. With the improvement of modern analytical methods and experimental techniques, the research on trace elements will be further deepened, and the above classification methods will inevitably be perfected and revised.
Second, the main physiological functions of essential trace elements in animals
1. Iron (Fe)
Fe is widely distributed in various tissues of animals and plays an important physiological function in animals. Mainly in the following aspects:
(1) Fe is a component of various compounds required for the oxidation and energy supply process of animals, and is related to the activity of some enzymes. For example, Fe participates in the composition of hemoglobin and myoglobin, and plays the role of transporting oxygen and dioxane carbon in the body: participating in the synthesis of cytochrome oxidase, peroxidase and catalase, and maintaining or enhancing acetyl-CoA, The activity of cytochrome reductase ensures that the tricarboxylic acid cycle in the body can proceed normally. In the absence of Fe or Fe, the formation and activity of these components are severely affected, resulting in disorder of oxygen transport, storage, transport and release of carbon dioxide, and redox process of peroxide.
(2) Fe can affect the self-mass synthesis and immune function of eggs in animals. When the amount of Fe in the animal is at a normal level, the phosphorus can enter the DNA of the liver cell at a normal speed, thereby maintaining the normal development and renewal of the liver tissue. In the absence of Fe, the synthesis of DNA in the group is inhibited by the lack of phosphorus, and mitochondria and microsomes in hepatocytes and other tissue cells are abnormal. Thereby affecting the synthesis of protein and the utilization of energy, the animal has anemia and weight loss.
(3) The relationship between Fe and energy metabolism. As a component of cytochromes, Fe participates in the redox-energy process in animal cells. The cytochrome first obtains a low-cost Fe atom from the middle of the tricarboxylic acid cycle to a high-Fe atom. After leaving the mitochondrial membrane, the high-priced Fe is converted to divalent Fe under the cytochrome oxidase. The removed electrons are then transferred to the hydrogen atoms removed from the Krebs cycle, and the energy released from the oxidized synthetic water transported from the lungs by hemoglobin is used to form high-energy phosphate for muscle contraction and other metabolism. The need for the process.
2. Copper (Cu)
Since the determination of Cu as an essential element in animals in the early 20th century, people have made great strides in the research and understanding of Cu, especially in recent decades, in the study of the role of Cu in animal body is more detailed and specific.
(1) Hematopoietic function of Cu and animal body. Cu has a close relationship with the hematopoietic process of the body. Low pigmented small cell anemia occurs in animals after Cu deficiency. Studies have shown that Cu participates in the platter process by affecting the absorption, release, transport and utilization of Fe. Appropriate amount of Cu can absorb the absorption of intestinal iron, promote the release of static Fe from the storage site into the bone marrow, and make the inorganic Fe become organic Fe, complete the exchange between the trivalent Fe and the divalent Fe, thereby facilitating the transportation of Fe. And use.
(2) Enzyme activity in Cu and animals. Cu is a constituent of many enzymes in the body, such as tyrosinase, ascorbate oxidase, uricase, and galactosin. These enzymes play an important catalytic role in the conversion of peroxide anion radicals into O2 and H2O2. In addition, Cu is also an important component of the superoxide dismutase and monoamine oxidase systems. These enzymes are mainly present in the body's elasticity and tissues, catalyzing the conversion of lysine residues in the elastin peptide chain to aldehyde groups, and performing aldol condensation or aldimines with similar aldehyde or amino groups of another peptide chain between molecules. Condensation, which in turn forms a covalent crosslinked structure between the elastin fibers. The elastic fibers are made in an insoluble state to maintain the toughness and elasticity of the structure. After Cu deficiency, the respiratory metabolism and division process of cytochrome cannot proceed normally.
(3) Cu and animal reproduction. Many studies in recent years have proved that Cu has a very close relationship with animal reproduction. Reproduction activities require more Cu than maintaining normal life activities. When the amount of Cu is normal, the pregnancy process of the animal can be maintained normally. After the lack of Cu, embryo death and absorption often occur, resulting in a decrease in the reproductive rate.
(4) Regulation mechanism of Cu and animals. Cu has a wide range of functions in the regulation mechanism in the body. First, Cu has special functions in maintaining the central nervous system and normal functions. Whether it is too little or too much, there will be pathological changes in the brain and brainstem. In the absence of Cu, brain tissue atrophy, degeneration of gray matter and self-quality. When there is too much Cu, brain tissue and nerve cells develop lesions, causing dysregulation and mental changes in the communist animals. Secondly, Cu can also affect the function of secretory glands in the body, so as to achieve the purpose of extensively regulating various activities of the body.
(5) The immune response of Cu to the animal's body. Newbeme is equal to the 1968 report that Cu has a close relationship with the body's immune function. Komegay et al. (1989) studied the effects of biotin and Cu addition on the performance of weaned piglets and the immune response to lysozyme, phytohemagglutinin and sheep erythrocytes. The result is that the addition of biotin can increase the immune response of piglets to sheep red blood cells, but not to increase the titer of lysozyme: while the addition of Cu tends to reduce the immune response to lysozyme and phytohemagglutinin, but does not affect the sheep. The immune response of red blood cells.
3. Zinc (Zn)
In animal life activities, Zn acts directly through certain enzymes in animals. Zn is involved not only in the metabolism of DNA, RNA, proteins, sugars and lipids, but also in the function and activity of hormones such as insulin, prostaglandins and gonadotropins. Therefore, Zn has a very important influence on animal growth and reproduction activities.
(1) Effect of Zn on the synthesis and activity of various enzymes in animals. Theoretical studies of modern animal histochemistry have found that Zn has at least two pathways to participate in the process of material metabolism and life activities in animals: one is through the formation of certain enzymes and the activation of certain enzymes; the other is the influence The configuration of certain enzyme organic molecular ligands. Since the structure or activity of more than 80 enzymes in animals is related to Zn, the former pathway is the main way in which Zn affects the body.
(2) Zn can promote the growth and development of animals. Zn can affect the division, growth and regeneration of animal cells, which is more important for the physiological and nutritional significance of young animals in the period of vigorous growth and development. Zn is a component of various enzymes and hormones in the body, especially the components constituting DNA polymerase and thymidine kinase, and thus closely related to the synthesis of nucleic acids and proteins in animals. In addition, the normal development of animal brain tissue and the ability to regenerate tissue wounds are also related to the nutritional status of Zn in animal body seas.
(3) Zn has a static effect on carbohydrates, fat and energy metabolism. Insulin is an extremely important hormone in animals that regulates blood sugar levels and promotes lipid metabolism. Although Zn does not participate in the formation of islet cord, it has the function of stabilizing insulin molecule, protecting it from being destroyed by insulinase and prolonging the function time of islet cord, thus enhancing the effect of insulinase-induced hypoglycemia. The effect of Zn on sugar, fat and energy metabolism in animals is mainly through the action of certain enzymes.
(4) Zn and animal reproduction. Zn exerts important physiological significance by affecting the development of sexual organs and the secretion of sex hormones in the normal development of sexual organs of animals and the normal functioning of sexual functions. As early as 1940, people obtained Zn to enhance the results of pituitary gonadotropin. Injecting Zn salt into the females in the resting period can stimulate the development of sputum and increase the weight of the uterus. On the other hand, the final stage of sperm maturation must also obtain enough Zn to be combined in large amounts into the semen to maintain the integrity of its epithelium, and the finalization of sperm differentiation.
(5) Zn and animal taste and appetite. The animal's taste and appetite are also closely related to the nutrition of Zn. The mechanism of action may be that Zn affects taste and appetite with a susceptor (gusfin), a salivary protein with two Zn ions in saliva. In recent years, it has been proved from experiments and pirates: after the lack of Zn in animals, the sense of sensation and appetite are reduced, and Zn can be improved after supplementation.
4. Manganese (Mn)
Mn is a trace element that is essential for animal growth and reproduction. Its important role in animals has been fully confirmed by recent studies.
(1) Metabolism of Mn and three major nutrients. The synergistic relationship with choline during fat metabolism in the body has been known for many years. Supplementation of Mn in Mn-deficient feedings can reduce fat deposition and reduce the thickness of the fat layer. However, there is still insufficient research on the mechanism by which Mn reduces body fat storage. In the process of carbohydrate metabolism, Mn is mainly in the multiple links of the Krebs cycle, which is beyond the action of enzyme activators. The effect of Mn on the nitrogen balance in animals has attracted more and more attention due to the lack of increasingly serious protein feeds. However, research on this aspect still needs to be explored in depth.
(2) Mn participates in the process of hematopoiesis and coagulation in the body. The effect of Mn on hematopoietic function in animals has already played a role in the early stages of their embryos. It has been reported that 12-15 days of embryonic liver has the ability to enrich Mn. The liver in this period is also the main organ of hematopoiesis. After administration of a small dose of Mn heat or Mn protein complex to anemia animals, blood red eggs, red blood cells (polychromatic erythrocytes), red blood cell volume, and circulating blood may be increased. There is also a close relationship between Mn and blood coagulation. The blood coagulation process of animals must have the presence of thrombin. Thrombin is converted from thrombin by Ca++ activation, and thrombin is a glycoprotein whose synthesis is affected by Mn.
(3) Maintain normal bone growth and ensure normal bone structure. Mn is involved in the synthesis of chondroitin sulfate in mucopolysaccharide, which is an important component of cartilage and bone tissue. The synthesis of chondroitin sulfate is hindered after Mn deficiency, resulting in impaired cartilage growth and abnormal bone formation.
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