Animals' intake, digestion and absorption of trace elements in food are related to various factors, the most important of which are the content and composition of trace elements in the diet and the synergy and antagonism between the elements. At the same time, trace elements are unstable and easy to combine, so the possibility of interaction is much greater than other substances. The interaction between the elements affects the potency of the trace elements added to the diet, which can occur in the feed, in the metabolic processes of the digestive tract tissue and tissue cells. Therefore, a thorough analysis of the synergistic antagonism between trace elements can be made to formulate a more reasonable ratio of trace elements with better utilization.
(1) Definition of synergy and antagonism
Synergies: The biological function of another element is enhanced by the action of certain elements, or the effective level of the element is increased. For example, trace elements related to hematopoiesis include copper, iron, cobalt, manganese and other elements, which act on different parts of hematopoiesis and cooperate with each other to complete hematopoietic function.
Antagonism: It means that in the digestive tract of animals, the elements inhibit each other's absorption; they have opposite effects on each other's physiological and biochemical functions in animals. Antagonism is mostly unilateral, but it can also be two-sided.
(2) Classification of synergy
1. Synergistic effect of trace elements in the digestive tract:
(1) Direct synergy between elements, the level of absorption is determined by the proportion of each element in the chyme and feed. Such as the synergy between calcium and phosphorus, sodium and chlorine, zinc and molybdenum in the diet.
(2) Indirect synergy occurs through the action of intermediate products of the phosphorylation process in the intestinal wall and the action of digestive enzymes. Such as phosphorus, zinc, cobalt, etc., can regulate the phosphorylation process in the intestinal wall, affecting the activity of certain digestive enzymes and affecting the release of elements in the feed and the absorption of other elements in the digestive tract. The interaction between iodine and selenium is also manifested by the effects of related enzymes and hormones.
(3) The interaction between trace elements and the anterior stomach of the ruminant and the microflora in the intestine promotes indirect synergy between its growth and activity. For example, cobalt can enhance the biosynthesis process while stimulating microbial growth.
2, the synergistic effect of trace elements on tissue cell level metabolism:
(1) Direct synergy in the process of structure formation
In the formation of hydroxyapatite (used for bone tissue repair), an important component of animal bone tissue, Fe and Cu are involved in the synthesis of hemoglobin; in the liver RNA molecular configuration, the interaction between Mn and Zn.
(2) Elements that are simultaneously involved in the active center of the enzyme (Fe and Mo in xanthine and aldehyde oxidase, Cu and Fe in cytochrome oxidase).
(3) Trace elements are required to participate in the synthesis process during the activation and synthesis of the enzyme system.
(III) Classification of Antagonism
1. Antagonism of trace elements in the digestive tract
(1) A simple chemical reaction occurs between elements. For example, too much magnesium in the diet can form magnesium phosphate in the digestive tract, thereby hindering the absorption of phosphorus. Sulfur and copper can act to produce copper sulfide, which reduces the absorption and utilization of copper.
(2) Adsorption by colloidal particles. For example, iron and manganese can be immobilized on the surface of the insoluble magnesium salt or aluminum salt, thereby reducing the absorption of iron and manganese in the digestive tract.
(3) The ions compete for the carrier on the intestinal wall. For example, competitive antagonism of copper and zinc.
2, the antagonism of trace elements in the process of tissue and cell metabolism
(1) Simple inorganic ions and complex inorganic ions directly antagonize each other. For example, the relationship between copper and molybdenum, increasing the content of one element in the diet, causes a decrease in the content of another element in the tissue.
(2) The active center of the inter-ion co-competitive enzyme system produces antagonism. For example, in the metalloenzyme complex of alkaline phosphatase, magnesium ions compete with manganese ions.
(3) Antagonism caused by the combination of various elements in the blood with the same carrier. For example, iron and zinc can competitively bind to transferrin in plasma.
(4) Interaction between trace elements
1, copper
Copper and zinc
The absorption sites of copper and zinc are in the small intestine, and the two can compete with each other in the intestinal mucosa or metallothionein, thereby inhibiting absorption. When fed with high levels of zinc, serum, liver copper levels are reduced, copper absorption is reduced, ceruloplasmin activity is reduced, and copper deficiency anemia is produced. Copper and zinc can also induce the synthesis of a metallothionein in the intestinal mucosa, which can bind to multiple metal ions, and the copper binding ability is stronger than that of zinc, so copper is more stable in combination with metallothionein. This causes copper ions to be trapped on the surface of the intestine, blocking their transport to the outside of the cell, and eventually escaping into the feces with the loss of intestinal epithelial cells, which prevents and reduces the absorption of copper. It has been found that when Zn/Cu>10, it can cause nutritional disorders. When fed with excess copper, it inhibits zinc uptake. When Cu/Zn>1, it also causes nutritional disorders. For example, to avoid the economic loss caused by the imbalance of copper and zinc ratio to the cow, it is recommended that Zn/Cu = 4:1 is more suitable. Therefore, the appropriate ratio of copper to zinc can weigh the absorption and utilization of both.
Copper and iron
Copper has a very close relationship with iron. As a mediator of hematopoietic response, copper catalyzes the synthesis of iron-producing hemoglobin and red blood cells, and promotes the absorption, transport and utilization of iron. Because the absorption form of iron is Fe2+, Fe3+ is transported during transportation, and iron in feed is mostly Fe3+. Plasma ceruloplasmin can catalyze the reduction of Fe3+ to Fe2+. As a component of ceruloplasmin, copper lacks ceruloplasmin deficiency and causes iron absorption and utilization disorders. Copper can also convert inorganic iron to organic iron Fe2+. Promote iron into the bone marrow from storage sites, accelerate the synthesis of hemoglobin and porphyrin, and accelerate the utilization of iron. In addition, the addition of iron salts to sheep and cattle inhibits copper metabolism, and the addition of Fe2O3 to sheep diets inhibits copper absorption. For example, in areas heavily contaminated with copper, the addition of ferrous sulfate to livestock and poultry diets helps prevent copper poisoning. Iron-rich soils can have a similar effect. Therefore, in areas where copper may be scarce, it is not advisable to use iron-containing additives to feed sheep and cattle. For example, the proportion of iron and copper ingested by cows is more suitable for Fe/Cu=40:1.
In addition, the content of iron in diet and drinking water significantly affected the content of copper in the liver. With the increase of iron content in the diet, the storage of liver copper decreased significantly. Feeding iron containing 1400 mg/kg of yak will deplete the copper storage in the liver (Arc, 1980). When the iron content of the diet increases from 500 mg/kg to 800 mg/kg within 8 weeks, the liver copper storage It dropped sharply from 134 mg/kg to 16 (Phillppo et al., 1987). There is also an interaction between high iron and high sulfur in the diet, and the inhibition of copper absorption is greater when both are present (Underword and Suttle, 1999).
Copper and cadmium, mercury, silver
Heavy metal elements such as cadmium, mercury and silver have strong antagonistic effects on copper. Cadmium can inhibit the absorption of copper. When copper is at a critical intake, even a small increase in cadmium intake can have a detrimental effect on copper metabolism. Both silver and mercury can antagonize the absorption of copper, but its effect is not as significant as cadmium. The principle of antagonizing copper by elements such as cadmium and zinc is to compete for the position of the protein-bound metal. The Starcher study reported that a unique metal-binding protein was found in the duodenum of chickens and proved to bind to copper and to zinc and cadmium.
Copper and sulfur, molybdenum
The presence of sulfur and molybdenum in the diet reduces the absorption of copper. Sulfur in the diet can be converted to sulfide in the rumen, leading to the formation of copper sulfide precipitates, hindering the absorption and utilization of copper (Bird, 1970). According to Allen and Gawthorne (1987), sulfur and molybdenum form thiomolybdate in the rumen solid phase chyme, which does not dissolve the complex at the height of the copper bond, thereby reducing the supply of absorbable copper. This is a chemical reaction between the copper, sulfur and molybdenum elements in the rumen that hinders the utilization of copper and also blocks the absorption and utilization of copper by intestinal mucosal cells. Another study suggests that some of the molybdenum sulfide absorbed by the body can bind to plasma albumin in the blood, which in turn affects the normal biological function of copper, or indirectly inhibits some copper-dependent enzyme activities. Therefore, the ratio of copper to molybdenum in ruminant diets is 4:1 - 6:1, and Cu/Mo = 6:1 is the best among dairy cows.
Different types of dietary roughage, sulfur and molybdenum have different effects on copper absorption rate. The utilization rate of copper in silage is not affected by molybdenum level, and it is affected by sulfur level. The inhibition of molybdenum in hay is relatively small. For fresh forages, regardless of the concentration of sulphur and molybdenum in the diet, the percentage of available copper is lower than that of hay or silage. Increasing the percentage of sulphur and molybdenum can significantly affect the absorbability of copper.
2, iron
Iron and zinc
Iron and zinc are trace elements with high levels in animals. Antagonism of the two elements is more likely to occur in organisms, and zinc competitively binds to transferrin in plasma. Tests by Settlemire and Matrone have shown that high zinc reduces the liver transferrin content, indicating that high zinc can interfere with ferritin binding and release of iron. Therefore, the zinc content in the feed is too high, which can cause a series of iron deficiency diseases such as anemia, slow growth, and low disease resistance. On the contrary, the excessive iron content in the feed will also affect the absorption and utilization of zinc and cause zinc deficiency in livestock and poultry. Iron also has an inhibitory effect on the absorption and utilization of zinc. The inorganic iron and zinc in the food can inhibit each other. It has been observed that small doses of zinc can reduce iron absorption, but organic iron and zinc do not affect each other. When the iron-zinc ratio in food is gradually increased (from Fe/Zn = 1:1 to 3:1), the concentration of plasma zinc gradually decreases, but when iron is added in the form of heme, even if Fe/Zn is 3:1, It does not affect the absorption of zinc, and the interaction between them may be related to the form of existence. Iron has an effect on the absorption and utilization of zinc, and the effect of ferrous iron is greater than that of trivalent iron. Cox and Harris found that the iron storage capacity of ferritin and hemosiderin decreased at high zinc levels.
Iron and manganese
Iron and manganese have the same electron orbital, configuration and coordination number, which can interfere with each other in the absorption process of the digestive tract and assist in hematopoiesis. When a large amount of manganese is given to animals, most animals develop anemia, which is characterized by decreased iron content in serum and various organs, delayed formation of hemoglobin, and increased manganese concentration in tissues, indicating that the large supply of manganese inhibits the absorption and utilization of iron. Iron deficiency can increase manganese absorption, but high iron inhibits manganese absorption and utilization.
Iron and Cadmium
Cadmium affects iron metabolism, causing insufficient hemoglobin synthesis, causing anemia, bone metabolism disorders, and even osteopenia.
3, zinc
Zinc and cadmium
Cadmium competes with zinc at the molecular level and can interfere with inhibition of copper absorption. Cadmium and zinc are the same ionic ions, and there is a strong competitive inhibition in the intestinal absorption process. A large amount of cadmium enters the body, inhibiting the absorption of zinc and reducing the zinc content in the body. When symptoms of cadmium poisoning occur, the toxicity of cadmium can be inhibited or reduced after a certain concentration of zinc is administered.
Zinc and Manganese
Burch et al. showed that the manganese concentration in piglets was significantly lower than that in the zinc-added control group. Adding zinc to the hen's feed improves eggshell quality and improves immunity. However, most studies have shown that zinc can only be effective when added to the diet of laying hens at the same time as manganese (Holder, 1978; Hunntley, 1978). That is to say, zinc and manganese in the diet of the laying hen can synergistically improve the quality of the eggshell. Tahatapob (1985) conducted an in-depth study on the relationship between manganese and zinc, and believed that 55-75 mg/kg of manganese and zinc gave the eggshell a higher calcium to nitrogen ratio and increased uronic acid content, thereby improving eggshell quality. Moreover, the addition of organic zinc and manganese in high-calcium feed has high bioavailability, which can significantly improve the quality of the eggshell. Feeding at night can help the gut to release calcium continuously, thereby improving the quality of the eggshell. Tests have shown that in the diet of AA broiler chickens, when the level of zinc is fixed, the manganese weight is lower than 130mg/kg (excluding the manganese content in the basal diet), and the weight of the broiler chicken increases with the increase of the manganese level. increase.
4, selenium
Selenium and arsenic
Selenium and arsenic are adjacent to the same period in the periodic table. Studies on selenium-arsenic interactions have been ongoing for a long time, including the antagonism of arsenic to selenium toxicity, as well as the protective effect of selenium on arsenic poisoning, and the synergistic effect of selenium-arsenic under certain special conditions. It is indicated that with the change of concentration of arsenic and selenium, synergistic effect and antagonism can be seen between selenium and arsenic. Especially when both elements are in the range of toxic concentration, synergistic effect is produced.
Selenium and Cadmium
Cadmium poisoning in cattle and pigs, often manifested as selenium deficiency, selenium can prevent the occurrence of the disease.
5, chrome
Chromium and iron
Chromium and iron have an antagonistic effect. After absorption through the intestine, chromium enters the combination of plasma and protein to transport chromium to the liver and the whole body. If the blood iron is too much, the protein is saturated, the chromium ion binds to the protein, and the chromium ion and The protein binding site is completely occupied by iron ions, so that the chromium ions can not bind to the protein, and the transportation, metabolism and utilization of the chromium ions will also be difficult, and finally lead to physiological dysfunction and pathological changes.
In short, because different animals have different needs for different kinds of trace elements in different physiological stages, and the utilization rate and biological potency of different kinds of trace elements are different, we should pay attention to the synergistic antagonism between trace elements in actual production. Avoid the waste of trace elements and reduce the use effect in the animal body.
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