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. A good way to find out is to have your vet take blood samples, liver biopsies or urine samples from live animals. This type of sampling is usually adequate to measure the level of most minerals in the body, though illness may skew the results. Diarrhea, acidosis, stress, fever, trauma, etc. can alter the concentrations of certain minerals in body fluids and tissues.

If you are testing for mineral deficiencies it is important to test several animals in the herd and not just a sick one or one that died. Traditional recommendations were to check 10 animals or 10 percent of the herd, whichever is the most logical number for your herd size. But if you only have 20 cows, 10 percent (2 cows) is not an adequate number; you'd need to test at least 5 or 6 cows. At the other end of the spectrum, if you can get a good sampling of 10 cows from a 300-cow herd, this might be enough animals to test. There can be a lot of individual variation in cattle, so you need to make sure you have enough samples to get a true picture of the herd's mineral status.

Selenium Deficiency � The soils (and therefore the feeds) in many regions are low in selenium, and a few areas have too much. Selenium is a tricky element in the diet, since cattle can be 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 even loss of hooves.

Selenium, along with vitamin E, is crucial for producing an enzyme that protects muscle cells from damage during exercise, and is important for muscle function. 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 the 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 deficiencies are common in parts of 42 states, including the Northwest and northern California. Some soils are so deficient that supplementation is always needed, while other areas have adequate amounts, and some others have areas with toxic concentrations. In these regions livestock may be poisoned when they eat plants that are selenium accumulators.

Lack of selenium is much more common than toxicity, however. 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 their 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 sometimes develop if sulfur 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 some other plants. Cattle grazing legume pastures or feeds grown in soils that contains sulfur 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 less hay cuttings per season have time to accumulate more minerals. When in doubt, have feeds tested.

Copper Deficiency � Low copper levels in cattle can result in many problems�everything 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 the copper levels in your animals. When the deficiency is corrected, they do better and have fewer problems.

One of the most visible signs of copper deficiency is change in hair color. Black animals develop a red or gray tint and red animals become more bleached and light colored. The coat becomes dull instead of shiny, and the animals may be slow to shed in the spring. In young animals, copper deficiency can result in diarrhea and more incidence of calfhood diseases, lameness and poor response to vaccination. Affected animals may have a stiff gait and the ends of the cannon bones may be enlarged and painful, with sore fetlock joints. Pasterns may be upright and the calf seems to be walking on its toes. Bones may be weak and brittle, and easily broken. Heifers may be late reaching puberty and their fertility may be impaired, and 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 sulfur. Deficiency may be primary (when there's not enough copper in the soil or in plants grown on those soils) or secondary when other factors prevent utilization of copper. Some of the elements that bind with copper to prevent its absorption by the body include molybdenum, iron, zinc, sulfur, lead and calcium carbonate. In the West, many regions have problems due to presence of molybdenum. Red clover and other legumes are some of the plants that seem to accumulate molybdenum, and this may add to the problem in certain pastures. This is most common with alkaline soils, since molybdenum uptake is influenced by the 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 high ground or range pastures. When evaluating a forage sample for copper, always look at the copper to molybdenum ratio. If forages contains less than 8 to 10 parts per million of copper, they are borderline deficient. The problem is compounded when molybdenum levels are in excess of 1 to 3 parts per million or when the copper to molybdenum ratio falls below 3 (or 4) to 1.

Even if you don't think you have a copper problem, it pays to check. Many people think that if they keep cattle well fed and healthy, they won't have this problem. But 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 any obvious signs (like discolored hair). Cattle may have subtle symptoms such as more incidence of disease, increased numbers of animals that develop respiratory problems, or calves with diarrhea or disappointing weight gains.

Forage samples, blood tests or liver biopsies can help determine whether there's a problem. There are several strategies that can be used to correct a problem. 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 were notorious for 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 any deficiencies. Even a salt/mineral mix is not 100 percent effective because cattle have variable salt intake. Some animals will consume enough of it but others won't eat enough, and some will eat too much and risk poisoning. There's always some risk of copper toxicity with long-term over-supplementation.

It can be a challenge to get calves to eat enough mineral. Some stockmen think that if the cows are eating it the calves will be ok, but minerals are not transferred through the milk very well. Zinc levels in calves, for instance, often drop dramatically after they are born. To make sure all calves have adequate trace minerals, some stockmen give each calf an injectable product before the grazing season.

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.

Iodine Deficiency � Iodine is another trace mineral that is very important, yet toxic if consumed 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, and the rate at which the body breaks down and eliminates waste materials. 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. Iodine deficient cows may be infertile or give birth to hairless, weak or stillborn calves. Bulls may have lower fertility. Many areas of the U.S are deficient in iodine, so this important trace mineral is often added to protein supplements, salt mixes and salt blocks.