Cattle require the proper balance of water, energy, protein, vitamins and minerals to achieve optimal production. In some cases, all the necessary vitamins and minerals are present in the forage. However, it is not unusual for foragebased diets to be deficient in one or more minerals and vitamin A.
Cattle usually require some form of mineral supplementation during all times of the year. The required minerals are divided into major (macro) and trace (micro) minerals. Major minerals are reported as a percentage of the diet. The major minerals include sodium, chlorine, potassium, calcium, phosphorus, mag - nesium and sulfur. Trace minerals are required at much lower levels than the major minerals but are just as essential. Trace minerals are commonly reported as parts per million (ppm). Required trace minerals include zinc, copper, selenium, manganese, iron, nickel, cobalt, molybdenum and iodine.
Salt (sodium chloride). Supplemental salt is almost always required by the beef herd. The only exception is when water is very high in salt or with forages that are grown on very salty soils.
Phosphorus. Phosphorus is often deficient in forages for lactating cows with superior milking ability. Phosphorus is one of the structural components of the skeletal system, and levels build up when cows are grazing lush forages that contain phosphorus at levels above require ments. Some of the phosphorus in bone can be mobilized during early lactation to overcome shortfalls in intake, but prolonged dietary deficiency has been reported to result in depressed reproductive efficiency and milk production.
Calcium. Calcium is usually not deficient in grass forages fed to beef cattle in Arkansas. In addition, legumes such as alfalfa and clover are high in calcium. Like phosphorus, calcium is a structural part of bone, so temporary shortfalls in the diet can be overcome by the animal mobilizing some of the calcium in bone.
Magnesium. Forages contain adequate magnesium during most of the year, but levels can be very low during times of rapid growth in the spring and fall, especially in well-fertilized pastures. There can also be high levels of potassium in forage at this time, which can interfere with the absorption of mag - nesium. The low level of magnesium in forage often corresponds to calving seasons and the onset of lactation, which is when cow requirements are highest. These factors and very low body mag nesium stores can lead to acute mag - nesium deficiency, a malady known as grass tetany. Supplementation with magnesium oxide is recommended for 30 days prior to calving and during the first three months of lactation. Provide a mineral with enough magnesium (at least 10 percent in a 4-ounce/head/day mineral) with less attention paid to phosphorus during periods that promote magnesium deficiency.
Potassium. Potassium is usually excessive in most forages in Arkansas, with the exception of weathered stockpiled forages. Potassium is primarily present as an electrolyte in body fluids, so there is little storage.
Sulfur. Sulfur is a component of several amino acids that are the building blocks of protein. Sulfur, other than that fed in the form of protein, is usually needed only when diets contain sub stantial amounts of nonprotein nitrogen (NPN).
Trace Mineral. Because of the low level in forages and lower bioavailability, trace mineral supplements are usually formulated to meet at least 100 percent of beef cattle requirements.
Zinc. Zinc is deficient in many Arkansas forages. Forty percent of hays tested at the U of A were deficient in zinc. Zinc is a part of many important enzyme systems in the body, and its deficiency leads to depressed feed intake and growth rate, an abnormal hair coat and skin lesions. Zinc is important in male reproduction. An adequate zinc status is also needed for normal immune response. Storage of zinc is minimal, and deficiencies occur rapidly following introduction of animals to a diet severely deficient in zinc. Zinc methionine, an organic form of zinc, has improved performance in feedlot cattle and in cattle grazing forages already containing adequate levels of zinc. Zinc methionine can help overcome foot problems in cattle. Veterinarians and nutritionists recommend feeding zinc methionine as an aid in controlling, and even treating, foot rot in beef cattle. High levels of iron in the diet interfere with the absorption of zinc and increase the dietary requirement.
Copper. Copper, like zinc, is deficient in many areas of Arkansas (52 percent of hays tested were low in copper). It also comprises an essential part of many different enzymes in the body. Copper is important for adequate growth, reproduction and immunity. Some breeds have been shown to be more prone to copper deficiencies. Unlike zinc, copper is stored tenaciously in the liver, and levels build up rapidly when animals are fed high levels of copper. Copper is extremely toxic to sheep, so many supplements sold to cattle producers contain little copper, primarily to prevent liability of the supplement manufacturer in case the product is fed to sheep. Cattle producers should avoid using a low copper mineral unless complementary grazing programs with sheep are being used. Copper oxide should be avoided as a copper source because of its poor bioavailability, which will affect the level of copper required in supplements. High levels of molybdenum, sulfur, iron or zinc in the diet interfere with normal copper absorption and metabolism.
Selenium. Selenium levels are marginal to deficient throughout Arkansas. Sixty-two percent of hays tested for selenium were deficient. Severe selenium deficiency results in white muscle disease in calves, which is characterized by stiffness and heart failure. The activity of selenium is related to vitamin E, and supplementation with either will help prevent white muscle disease. However, since vitamin E levels are normally not a problem, selenium deficiency is usually the underlying problem. Marginal selenium deficiency can result in retained placenta, impaired fertility, silent heats and unthrifty weak calves with poor immune response (resulting in high preweaning death losses). Selenium can be provided in mineral mixes or in an injectable form.
Manganese. Manganese levels in forages vary considerably, depending on the soils on which they are produced. Manganese is a part of several important enzyme systems. A deficiency may result in impaired reproductive performance in both cows and bulls and in the birth of deformed calves.
Cobalt. Cobalt is needed only for the ruminal synthesis of vitamin B12. Cobalt requirements are higher when cattle are fed high-grain diets, because more B12 is required to metabolize the end products of rumen fermentation. Cobalt may be very deficient in some soils, so including it in trace mineral supplements is a sound practice.
Iron. Iron is a part of hemoglobin, which transports oxygen to body tissues. Since most forages contain high levels of iron and because substantial amounts of soil are consumed during grazing, iron is almost never deficient in cattle fed forage-based diets. A more common problem with iron is that it may be excessively high in forages or in drinking water, which can interfere with the absorption of copper and zinc.
Iodine. Iodine makes up part of the thyroid hormones. A deficiency results in a condition known as goiter, which is actually an enlarged thyroid gland. Iodine is normally included in trace mineral supplements. The following are recommendations for a mineral supplementation.