Copper is an essential element for normal growth and production of dairy cows. Due to the complex natural conditions, different soil types, and different plant species, the trace element copper contained in forage materials is very different, and there are problems of lack of and excess in different areas. There are many factors affecting the copper absorption rate. Therefore, the requirement of trace element copper and its influencing factors are described in this paper.
Copper's nutritional and physiological functions Copper is an important component of superoxide dismutase, copper-induced metallothionein, and plasma ceruloplasmin. These enzymes protect cells from the toxic effects of oxygen metabolism and maintain the integrity of cellular structures and functions; copper Can influence the absorption and transportation of iron, promote inorganic iron to become organic iron, promote iron storage in bone marrow, accelerate the synthesis of hemoglobin and porphyrin, promote the maturation and release of immature red blood cells, and play a positive role in hematopoiesis; copper participates in the formation of bones Copper is a component of tyrosinase that promotes melanin formation and pigmentation; copper oxidizes sulfhydryl groups to disulfide bonds and promotes cross-linking of disulfide groups to promote coat growth; copper is cytochrome C Oxidase cofactors participate in energy metabolism; copper and ceruloplasmin have important significance on the defense function of the body; copper can promote pituitary release of growth hormone, thyrotropin, luteinizing hormone, and adrenocorticotropic hormone, affecting the adrenal cortex Synthesis of steroids and catechol moieties, which affects the productivity of dairy cows; copper is heavy in maintaining the nervous system To play a role, copper can increase the activity of digestive enzymes, or adjust the intestinal micro-ecology and increase the mitogenic factors in the blood, stimulate pituitary cells to secrete growth hormone, and then promote growth; Copper has a significant effect on improving feed conversion and milk yield.
Copper demand The endogenous loss of copper is approximately 71 μg/kg body weight. The amount of copper in colostrum is about 0.6 mg/kg, and the amount of copper in regular milk is about 0.15 mg/kg, which is 50% higher than the 0.10 mg/kg milk produced in the 1980 edition of ARC. The amount of copper needed for absorption is 0.5 mg/day for 100 days before pregnancy, 1.5 mg/day for 100 days to 225 days of pregnancy, and 2 mg/day for 225 days after pregnancy. A cow cow with a weight of 300 kg and an average daily gain of 0.7 kg has a copper requirement of 12 mg/kg diet, a body weight of 500 kg, an average daily gain of 0.5 kg, and a copper requirement for young cows of 250 days of pregnancy The cow's copper requirement was 15.7 mg/kg and body weight was 650 kg for 15.2/kg, weight 650 kg, and daily milk production 40 kg. The cow copper requirement for the 250 days of gestation was 13.7 mg/kg.
Factors Affecting Copper Demand Dietary copper requirements for maintenance, growth, and lactation vary with the age of the animal, the chemical form of copper in the feed, and whether there is a substance in the feed that interferes with copper absorption.
Different varieties of dairy cows have different copper needs and tolerances. Juan cattle have a higher ability to deposit copper in the liver than Holstein, and therefore have low tolerance to copper toxicity.
With the growth of rumen microorganisms, rumen function has been perfected, and the absorption efficiency of copper has declined rapidly. The absorption rate of dietary copper in newborn yak can reach 70%, and the absorption efficiency of copper within 6 weeks after birth (before weaning) is 60%. By adulthood, the absorption efficiency of dietary copper by cattle is only 1% to 5%.
Feeding methods Grazing livestock requires twice as much copper as feeding. Because of the ingestion of grasses when grazing feed forage (accounting for 10% of dry matter intake), the copper absorption efficiency is reduced by 50%.
Copper sources often supplement copper in the form of inorganic salts such as copper sulfate, copper oxide, and copper carbonate, among which copper sulfate has a higher biological potency, copper carbonate is centered, and copper oxide is lower. Because copper oxide cannot be dissolved, it is generally not used as a copper source, but copper oxide copper wire degrades slowly in the rumen and can supplement copper for livestock for a long time. Copper chloride is 20% more available than copper sulfate. Since inorganic copper is susceptible to the effects of molybdenum in feed and resistance to copper orange, people began to study the effect of organic copper on the absorption rate. According to studies, the copper protein chelate has higher absorption efficiency than copper sulfate. When calves are fed high-molybdenum diets, copper protein compounds are more easily utilized by the body than copper sulfate. However, it has been found that the absorption efficiency of copper protein compounds and copper sulfate is similar when feeding high-molybdenum diets to fattening calves.
The presence of sulfur and molybdenum in the diets of sulfur and molybdenum reduces the absorption of copper. Sulfur in diets can be converted into sulphides in the rumen, leading to the formation of copper sulphide precipitates that impede the absorption and utilization of copper. Researchers believe that sulfur and molybdenum form tetrathiomolybdate in the rumen solid-phase chyme, which combines with copper to form highly insoluble complexes, thereby reducing the amount of copper available for absorption. Different types of dietary roughage, sulfur and molybdenum have different effects on the absorption rate of copper. The utilization rate of copper in silage is not affected by the level of molybdenum, and is greatly affected by sulfur level, when the sulfur content is 0.2% The available copper is 5.5%, but when the sulfur content is 0.4%, the available copper drops to about 1.5%. The inhibitory effect of molybdenum in hay is relatively small. When the sulfur content increases from 0.2% to 0.4%, the percentage of available copper decreases by 20% to 30%. For fresh forage grass, the percentage of available copper is lower than that of hay or silage regardless of the concentration of sulfur and molybdenum in the diet. Increasing the percentage of sulfur and molybdenum will significantly affect the absorbability of copper. When the level of dietary molybdenum was low, the increase of molybdenum level had the greatest inhibitory effect on copper absorption. When the level of dietary molybdenum reached 4 mg/DM-5 mg/kg, the inhibition was stable, and the higher dietary molybdenum concentration was found in copper. The effect of absorbability is not significant.
High-zinc dietary zinc induces the increase of metallothionein attached to intestinal parietal cells, which binds to copper and binds it to the surface of the intestine. The bound copper eventually falls into the feces as the intestinal epithelial cells fall off. Studies have found that there is a negative linear correlation between dietary zinc concentration and the amount of copper in the liver. When the lambs were fed with 40 mg zinc, 220 mg zinc and 420 mg zinc diet per kilogram, the survival rate of copper in the liver was 4%, 2.8% and 1.5%, indicating that the dietary zinc content was greater than 40 mg. At 100 kg/kg, the absorption efficiency of copper decreases by 16% for every 100 mg/kg increase in zinc. When zinc was added to adult lactating cows to a level of 2000 mg/kg, plasma copper levels decreased, but plasma copper did not change when zinc was added at 1000 mg/kg. It shows that zinc will not become the main factor affecting copper absorption under actual production conditions.
The content of iron in the diets and drinking water of high-speed iron diets significantly affected the content of hepatic copper. With the increase of dietary iron content, the liver copper reserves decreased significantly. Calves consume 1,400 mg/kg ferric iron diet and deplete the liver’s copper reserves. When the dietary iron content was 500 mg/kg DM within 8 weeks, the liver copper reserves dropped drastically from 134 mg/kg DM. 16 mg/kg DM. There is an interaction between high-iron and high-sulfur diets, and the inhibition of copper absorption is greater when both are present.
The addition of calcium to high-calcium diets will affect copper absorption efficiency. Copper absorption rate decreased from 0.70% to 0.95%, but in other studies dietary calcium levels had no effect on copper absorption.
Copper deficiency Symptoms The normal copper concentration in the liver is 200 mg DM to 300 mg DM per kilogram. Copper deficiency occurs when the liver copper concentration is less than 20 mg/kg DM (ie, 5 mg/kg wet weight) or the copper concentration in the plasma is less than 0.5 mg/L. The typical early symptoms are hair pigmentation disorders, especially around the eyes, the coat is lackluster, and the mess is rough, the red hair becomes light rust red, and even yellow, black becomes pale gray; the oxidative function of the tissue cells is reduced, and the sulphhydramide in keratin The base is difficult to oxidize to H-thiol affecting hair growth. Cause iron absorption and utilization barriers, so that Fe3 + can not become energy into Fe2 and difficult to synthesis of hemoglobin, the emergence of small red blood cell hypochromic anemia; lysine oxidase activity and monoamine oxidase activity decreased intravascular lock chain and isosteric chain increased, blood vessels Decrease in wall elasticity, causing arterial rupture and decreased collagen stability in the bones, resulting in brittle bones and osteoporosis; decreased immune function, decreased ability of neutrophils to kill invading microorganisms, leading to vulnerability of the body to infection, and poor ovarian function. The estrus was delayed or blocked, the conception rate was low, the delivery was difficult, and the placenta was not lower; the nerves were demyelinated and the nervous system was damaged. The patient showed ataxia and hind limb paralysis. Cows grazing on copper-deficient or high molybdenum pastures were found to have diarrhea within 8 days to 10 days. Faecal samples were presented as water samples, followed by yellow-green to black. Copper deficiency in dairy cows is often caused by too low levels of copper in the forage or excessive levels of molybdenum or sulfate.
Before the apparent toxicity of copper from over-cooked cows of copper is evident, copper will deposit in the liver, and stress or other factors will cause a large amount of copper to be suddenly released from the liver into the blood, causing hemolysis, jaundice, and methemoglobinemia. Symptoms, hemoglobinuria, systemic jaundice, large areas of gangrene, and often lead to death. Adding 4 to 5 times the required amount of copper in cattle diets may result in chronic poisoning.
Conclusion According to various factors affecting copper demand, the amount of copper added is limited by rumen microbes and other mineral salts. Because copper has a toxic effect on rumen microorganisms, when copper is used in excess of a limited amount, microbial activity is reduced or died, affecting feed utilization. In addition, other mineral ions in the diet, such as molybdenum, sulfur, iron, zinc, calcium and other elements that are antagonistic to copper, increase the demand for copper. The author believes that the focus on organic copper and coated copper should not only reduce the toxic effects of copper on the rumen microorganisms, but also reduce the interaction between copper and other ions, thereby increasing the utilization of copper, and can also be obtained without affecting copper absorption. The actual amount of cow's copper needed after the factor.
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