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A Word About Minerals

Minerals are essential nutrients. Sodium, chlorine and potassium are crucial to maintain fluid balances in the body and blood. Sodium chloride (salt) should always be provided because cattle need more salt than occurs naturally in forages. Iron is an important component of red blood cells — enabling them to carry oxygen. Bone formation and milk production depend on calcium and phosphorus.

Calcium and phosphorus are called macro-minerals because they are required in fairly large amounts. Deficiency is generally not a problem because these minerals are often present in high levels in many feeds. Phosphorus supplementation is sometimes needed when cows are on dry grass or crop residues for long periods. Phosphorus levels in most harvested forages are generally adequate, unless it’s very poor-quality hay. Calcium is adequate in most forages, but is higher in alfalfa than in grass.

Trace minerals such as copper, iron, iodine, manganese, selenium and zinc are needed in very tiny amounts and also very important to health. Adequate levels of copper, zinc, manganese and selenium, for example, are crucial for a healthy immune system and optimum reproduction. According to Dr. Ron Skinner, a Montana rancher/veterinarian who does herd health/nutrition consulting, the most important time to supplement trace minerals is during the last 60 days of pregnancy when the fetus’s immune system is developing, and during the 60 to 90 days after calving — until the cow is rebred.

Mineral content of soil in which feed is grown determines availability of trace minerals in cattle diets. Soil and feed tests can be done to see if supplementation is needed. Keep in mind that overdoses of trace minerals are toxic.

If several animals in a herd experience health problems, poor fertility, poor response to vaccination, low weight gains or other signs of poor performance, a trace mineral deficiency may be to blame. One way to find out is to have your vet take blood samples, liver biopsies or urine samples from your animals. This sampling is usually adequate to measure the level of most minerals in the body, though illness may skew results. Diarrhea, acidosis, stress, fever, trauma, etc. can alter concentrations of certain minerals in body fluids and tissues.

When testing for mineral deficiencies it is important to test several animals and not just a sick one or one that died. “Traditional recommendations are to check 10 animals or 10 per cent of the herd, whichever is the most logical number for your herd size. But if you only have 20 cows, 10 per cent is only two cows and is not an adequate number; you’d need to test at least five or six cows,” says Skinner. “At the other end of the spectrum, if you get a good sampling of 10 cows from a 300-cow herd, this might be enough animals to test,” he says. You need to make sure you have enough samples to get a true picture of the herd’s mineral status.


Soils and feeds in many regions are low in selenium, and a few areas have too much. Cattle are unhealthy if they don’t have enough, and unhealthy if they get too much. Selenium is vital for proper body function, reproduction and a healthy immune system, but in excess it is toxic — causing loss of tail hair or hooves.

Selenium, along with vitamin E, is crucial to producing an enzyme that protects muscle cells from damage, and is important for muscle function. According to Dr. Steve Blezinger, a cattle nutritionist in Texas, selenium deficiency has been linked to reduced immunity (reducing the number and activity of cells required for normal immune response), decreased reproductive performance, retained placenta, and general poor performance.

Much of the U. S. and Canada is deficient in this important metalloid, and selenium leaches out of pastures and hayfields that have been irrigated for many years, making deficiency more pronounced. Soils in valleys with irrigation or heavy rainfall are often short on selenium, whereas foothills and uplands in the same region may have adequate amounts.

Selenium deficiency can lead to a wide variety of muscle diseases and weakness, reproductive problems, decrease in fertility, increased susceptibility to disease, and impaired heart function in young animals — especially if dams have inadequate selenium during pregnancy. Calves may be stillborn or die within a few days of birth. In some regions, white muscle disease can occur unless the dam was supplemented or the calf is given an injection of selenium at birth. Calves with white muscle disease may be weak, or die suddenly because the heart muscle is impaired.

Selenium deficiency may develop if sulphur or zinc inhibits proper utilization of selenium. Stockmen need to be careful when adding zinc to trace mineral supplements, and not overdo it.

Clover and alfalfa don’t pick up selenium as readily as grasses. Cattle grazing legume pastures or feeds grown in soils that contain sulphur may develop deficiency. Fields with high crop yield, intensive irrigation (that leaches selenium out of soil) and fertilization (which stimulates plants to grow faster, with less time to accumulate as much mineral from the soil) may contribute to selenium deficiency in some crops. The higher the crop yield, the smaller the concentration of selenium in each plant. Slower-growing plants with less yield per acre or fewer hay cuttings per season have time to accumulate more minerals.


Low copper levels in cattle can result in many problems — from poor hair coat to reduced weight gains, impaired immune system, broken bones, or lower reproduction rates. Often it’s a subtle problem you don’t suspect unless you check copper levels in your animals. When deficiency is corrected, they do better.

One of the most visible signs of copper deficiency is change in hair colour. Black animals develop a red tint and red animals become bleached and light coloured. The coat becomes dull and animals may be slow to shed in the spring. In young animals, copper deficiency can result in diarrhea and higher incidence of diseases, lameness and poor response to vaccination. Affected animals may have a stiff gait; the ends of the cannon bones may be enlarged and painful, with sore fetlock joints. Pasterns may be upright, with the calf walking on its toes. Bones may be weak and brittle. Heifers may be late reaching puberty and fertility may be impaired. Cows may be slow to cycle after calving.

Cattle may develop severe copper deficiency due to excess of other trace minerals such as molybdenum or sulphur. Deficiency may be primary when there’s not enough copper in the soil or plants grown on those soils, or secondary when other factors prevent utilization of copper. Elements that bind with copper to prevent absorption by the body include molybdenum, iron, zinc, sulphur, lead and calcium carbonate. Red clover and other legumes accumulate molybdenum, and this may cause a problem in certain pastures. This is most common with alkaline soils, since molybdenum uptake is influenced by pH of the soil.

Molybdenum is often an issue in valley bottoms since there’s more of this element in low areas than on uplands. Copper deficiency is more likely to occur in animals that graze the valley floor (or eat legume hay) than in animals grazing higher ground or range pastures. When evaluating a forage sample for copper, always look at the copper to molybdenum ratio. If forages contain less than eight to 10 parts per million of copper, they are borderline deficient. The problem is compounded when molybdenum levels are in excess of one to three parts per million or when the copper to molybdenum ratio falls below 3 to 1.

Even if you don’t think you have a copper problem, it pays to check. Copper levels in forages can vary from year to year, depending on weather conditions, soil factors, fertilization of fields and pastures, etc. Another thing that makes it difficult to recognize a copper problem is that you often don’t see obvious signs (like discoloured hair). Cattle may have subtle symptoms such as higher incidence of disease, more respiratory problems, or calves with diarrhea or disappointing weight gains.

Forage samples, blood tests or liver biopsies can determine if there’s a problem. Several strategies can be used to correct a deficiency. You can supplement with extra copper in a loose salt/mineral mix, or individually dose each animal with oral drenching, copper boluses or injections. Some of the early copper injection products caused injection site swellings, but newer products such as Multimin (providing copper, selenium, zinc and manganese) are less irritating.

Trace mineral blocks, which some ranchers rely on, generally do not contain enough copper to correct deficiencies. Even a salt/mineral mix is not 100 per cent effective because cattle have variable salt intake. Some animals consume enough but others won’t, and some eat too much and risk poisoning. There’s always risk of copper toxicity with long-term over-supplementation.


According to Blezinger, several extensive forage studies have shown that zinc may be the most widely deficient trace mineral. Zinc is important for proper function of many body systems, including production of certain enzymes, male fertility, and hoof structure. “Zinc is deposited in high concentrations in the liver of the fetus, if the dam has adequate levels in her body, but liver levels decline between 30 days and nine months of age. Calves may approach weaning with marginal zinc levels. This poses a risk for weaning and feedlot situations due to zinc’s effect on appetite and immunity,” explains Blezinger. Signs of severe zinc deficiency include swollen feet with open lesions, excessive salivation, loss of hair, reduced appetite and feed intake, reduced feed efficiency and growth, and impaired immune response.

Even if calves have adequate levels of copper, zinc and selenium, stress (such as weaning) may still cause problems. If calves are short on these important elements they are even more at risk when stressed. This is often the cause of big “wrecks” at weaning. Even if they don’t get sick, they may not gain as well as they should. They may also be at risk for “silent pneumonia” which will lower weight gains.

It can be a challenge to get calves to eat enough mineral supplement. Even if their dams are eating it, trace minerals are not transferred through the milk very well. To make sure all calves have adequate trace minerals, some stockmen give each calf an injectable product soon after birth. Blezinger recommends incorporating an injectable product into management programs. “Periodically injecting the cows (with an injection 30 to 60 days prior to calving, and again 30 days prior to rebreeding) and the calves (at birth, and again just prior to weaning) will significantly improve trace mineral status and performance of cows and calves,” he says.


Iodine is another trace element that is very important, yet toxic in large amounts. Most of the iodine in the body is in the thyroid gland; it regulates metabolism and the rate at which the body converts simple compounds from food into energy and building blocks for body cells. Iodine-containing hormones influence metabolism, the birth process, and ability of newborn calves to withstand cold stress.

Iodine deficiency results in enlarged thyroid gland (goiter), seen as a lump on the underside of the neck. Iodinedeficient cows may be infertile or give birth to hairless, weak or stillborn calves. Bulls may have lower fertility. Many areas of the U. S. and Canada are deficient in iodine, so this important trace mineral is often added to protein supplements, salt mixes and salt blocks.

Trace minerals are crucial for keeping cattle healthy and performing optimally. Working with a cattle nutritionist to develop a mineral program specifically tailored to your region/ ranch and your herd’s needs — and working with a veterinarian if you suspect health issues may be due to deficiency problems — can have a huge impact on your profit or loss when raising cattle.



Dr. Steve Blezinger, a nutritional consultant in Sulfur Springs, Texas, says mineral supplementation of the pregnant cow is crucial to set the stage for health of her calf. Her mineral status has significant long-term effects on how the calf grows and develops. Trace mineral deficiencies may result in immune dysfunction, developmental abnormalities, and poor calf growth. “The developing fetus is totally dependent upon availability of essential nutrients from the dam’s blood. From conception through birth, and up to weaning age, the cow is either the sole source of nutrition the calf receives, or at least a significant part,” says Blezinger.

Trace mineral status affects a calf’s immune function and response to stress. “A study of beef calves from birth to feedlot found calves from mineral- supplemented cows had greater response to vaccines, lower rates of sickness, and fewer sick pulls. Healthy feedlot calves had higher serum concentrations of zinc than calves experiencing respiratory disease,” he says.

Adequate trace minerals in the cow’s diet during pregnancy are crucial, since copper, iron, manganese and zinc are being stored in the liver of the developing fetus. A deficiency in these minerals cannot be “caught up” by supplementing the cow after she calves, since these minerals are not passed through her milk, except colostrum. Until the calf starts consuming a mineral supplement on his own he will be deficient — unless he gained adequate reserves in his liver during his mother’s pregnancy and via her colostrum. This is why it is important to supply the cow with adequate minerals, and why some ranchers hedge their bets with injectable trace mineral supplements to make sure every cow has enough of these important nutrients during pregnancy.

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