100 Questions and Answers on Scientific Pig Farming, Part Ten: What Are the Uses of the Trace Elements Copper, Iron, Manganese, Zinc, Cobalt, Iodine and Selenium?

Copper is used in the body to synthesize hemoglobin and to synthesize and activate certain oxidase enzymes. Copper deficiency rarely occurs in pigs. When the diet contains 6 mg/kg of copper, it can meet the needs of suckling piglets; when the copper content in the diet reaches 15 mg/kg, it can meet the normal needs of growing pigs; when the copper content in the diet of pregnant sows and lactating sows reaches 60 mg/kg, it can increase the birth weight and weaning weight of piglets. A large number of studies have shown that high doses of copper have the effect of stimulating growth and improving feed utilization. After 119 trials, some researchers found that feeding 250 mg/kg of copper could increase the daily weight gain of pigs by 9.1% and improve feed utilization by 7.4%. Long-term use of high copper can cause copper poisoning and damage liver and kidney function. For this reason, the United States currently no longer advocates the use of high copper, and even the United Kingdom, which has always used high copper, has changed the high copper dose to 160 mg/kg. The suitable supplemental amount of copper sulfate is between 125-250 mg. In the formula provided for use by the premix produced by our farm, the copper content for piglets is 160 grams per ton of feed (contained in 160 g/ton of complete feed), that is, the copper content per kilogram of compound feed is 160 mg (160 PPM), and 250 mg per kilogram of complete feed is optimal. Trials have shown that adding 255 mg of copper per kilogram of compound feed increases pig growth rate by 17.4% compared with the control group and improves feed conversion by 16.9%. Too much will affect appetite and weight gain. Generally, feed-grade copper sulfate contains 25% copper, and the air-dried powder containing 5 crystal waters contains 24.5% copper. Check the instructions when using it.
Iron is a component of most metabolic enzymes in the body. It is also an important component of proteins such as hemoglobin, myoglobin, uterine ferritin and lactoferrin. The sensitivity of pigs to iron is shown by the fact that suckling piglets are prone to iron deficiency anemia. When the levels of calcium, phosphorus, manganese, copper, zinc and other elements in the diet are too high, iron absorption will be affected. The net iron requirements of piglets of different weeks of age are: 70.3 mg at 1 week of age, 111.6 mg at 2 weeks of age, 170.2 mg at 3 weeks of age, 230.4 mg at 4 weeks of age, and 294.3 mg at 5 weeks of age. Ferrous sulfate containing 5 crystal waters (FeSO4·5H2O) has an iron content of 22.5%; the air-dried powder generally contains 30% iron. See the instructions for details. What our factory originally provided for piglets was 144 PPM per kilogram of feed, that is, 144 grams per ton of complete feed.
Manganese is a component of several enzymes and participates in the metabolism of the three major substances: carbohydrates, fats and proteins. When pigs ingest insufficient manganese, growth and ossification are hindered, carcass fat deposition increases, and sow reproductive function declines. When dietary manganese drops from 36.95 mg/kg to 25.74 mg/kg, the above deficiency symptoms can be observed. At present, the suitable manganese content in pig diets cannot yet be determined, which is due to contradictory results from many trials. Therefore, the recommended manganese requirements for pigs vary, including 10 mg/kg, 55 mg/kg and 80 mg/kg. German experts proposed a requirement of 20 mg/kg dietary manganese for pigs over 20 kilograms, and 30 mg/kg dietary manganese from weaning to 20 kilograms body weight as well as for sows. The amount of manganese used for piglets provided by our factory is 50.52 g/ton of complete feed, that is, 50.5 PPM per kilogram of complete feed. Manganese sulfate containing one crystal water (MnSO4·H2O) has a manganese content of 31.8%. See the instructions for details. For suckling piglets, supplementing 2 mg of manganese sulfate per kilogram of body weight in the diet is better.
Zinc is a component of many enzymes in the body. The zinc requirement of growing pigs is 40-170 mg/kg, and that of sows is 80-100 mg/kg. The physiologically effective amount of zinc and the toxic dose differ greatly. Pigs can tolerate 20-30 times the normal requirement of zinc, so poisoning caused by excessive zinc rarely occurs; more common is zinc deficiency in the body. Zinc deficiency is mostly seen in growing-finishing pigs raised on concrete floors. Zinc deficiency causes dermatitis with parakeratosis, hinders growth, and causes poor hair growth, namely mange and skin lesions. Zinc sulfate containing 7 crystal waters (ZnSO4·7H2O) has a zinc content of 22.5%; the air-dried powder has a zinc content of 35%. See the product instructions. The zinc content used for piglets produced by our factory is 156 g/ton of complete feed, that is, 156 PPM per kilogram of feed. According to the literature, adding 100 mg of zinc sulfate per kilogram of compound feed gives better results: compared with the control group, the weight gain rate increases by 64.15% and feed conversion improves by 20.67%. Generally, adding four ten-thousandths of zinc sulfate to compound feed can basically meet the needs.
Cobalt can affect the synthesis of proteins, nucleic acids, glycogen and phospholipids in the form of vitamin B12. Pig diets usually do not lack cobalt. When the pig diet lacks cobalt, cobalt supplementation helps intestinal microorganisms synthesize VB12 and improves daily weight gain and feed utilization. There is not much research data on the cobalt requirement of pigs. It is generally believed that a diet containing 1 mg/kg of cobalt can avoid cobalt deficiency. 400 mg/kg of cobalt can cause poisoning in piglets. Selenium and vitamin E have a protective effect against cobalt poisoning. The premix we originally produced did not add cobalt, while the feed formula of Jiangxi Feed Factory includes cobalt.
Iodine exists in the thyroid gland and affects the body's substance and energy metabolism by participating in the formation of thyroxine. Insufficient iodine in pig diets can reduce thyroxine synthesis and affect the metabolism of organic substances and mineral trace elements in the body, thereby hindering growth and causing reproductive dysfunction. Iodine deficiency in pregnant sows increases the number of stillbirths and reduces milk yield, and piglets show enlarged thyroid glands, rough coats or no hair. An iodine content of 0.2-0.3 mg/kg in the diet can meet the needs of growing pigs. The iodine requirement of sows is 0.4-0.5 mg/kg. Calcium iodate, potassium iodate and calcium periodate are nutritive iodine salts and are more stable than sodium iodide and potassium iodide.
Selenium deficiency in pig diets can cause nutritional liver necrosis, mulberry heart disease or skeletal muscle degeneration, intestinal bleeding and other symptoms. Sudden death is a prominent feature of selenium deficiency syndrome in pigs. Vitamin E deficiency in the diet, or the appearance of environmental stress factors, can easily lead to selenium deficiency symptoms. Many trials have shown that a selenium content of 0.1-0.3 mg/kg in the diet can meet the normal needs of pigs. For mild selenium deficiency, 0.06 mg of selenium per kilogram of body weight can be injected as a supplement; for moderate selenium deficiency, 0.22 mg of selenium and 75 IU of vitamin E per kilogram of body weight can be injected as a supplement; for severe selenium deficiency, 1.1 mg of selenium and 75 IU of vitamin E per kilogram of body weight can be injected as a supplement, and the dietary selenium content should be kept at 0.6 mg/kg, while an additional 30 IU of vitamin E should be added.
Xiangying Breeding Pig Co., Ltd. uses 1% selenium agent, and piglets receive 20 g/ton of complete feed. Selenium and vitamin E have similar antioxidant effects, and the symptoms of selenium deficiency are similar to those of vitamin E deficiency. The selenium requirement of pigs is 0.1 mg per kilogram of dry feed, and poisoning can occur when it reaches 5 mg. In feed processing, appropriate methods must be adopted to prevent moisture and hygroscopicity, while also strictly controlling and rationally using the amount. (This content is excerpted from "100 Questions and Answers on Scientific Pig Farming", compiled and printed by the Yingtan City Association of Old Science and Technology Workers and authored by Zhang Genkai.)