Trace element deficiency and supplementation in cattle – part one

These elements are generally divided into two groups. Those whose requirements are measured in grammes are referred to as major minerals and include calcium, phosphorous, magnesium, potassium, chlorine and sulphur.

The other group’s requirements are measured in milligrammes and these are the trace elements. This group includes copper, cobalt, selenium, iodine, manganese, zinc and molybdenum. It is the latter group that we are interested in for the purposes of this article.

Copper

Copper is a very important nutrient and is involved as an activator of many enzymes in the body. It plays an important role in growth of bone and cartilage, in immune cell function, as an antioxidant, in blood formation and it plays many roles in cattle fertility.

There are many classic symptoms of copper deficiency in cattle and these include loss of hair pigmentation resulting in a reddish bleached coat or ‘‘spectacle eye’’, poor growth, depraved appetite, lameness, diarrhoea, anaemia, emaciation, ill thrift in young rapidly growing calves and sub-fertility.

Copper deficiency can arise through a primary deficiency or a secondary deficiency. A primary deficiency occurs when there is less than 10mg/kg DM of copper in the herbage. This is quite rare.

What is far more common in Ireland is secondary copper deficiency, and this arises when another element interferes with the absorption of copper in the gut of the animal.

In other words, there is sufficient copper in the diet but another element prevents the animal from utilising the copper. This is very common in Ireland.

The other elements that interfere with copper are molybdenum, sulphur and iron. They act by binding to the copper and making the copper insoluble and, thus, preventing the animal from absorbing the copper.

In an Irish context, most of the copper deficiency is actually due to high molybdenum levels, and this is far more common on pasture than on silage, because the silage can actually break down some of these insoluble complexes.

High iron levels can occur in silage if there is a lot of soil contamination of the silage.

Curiously, Jersey cattle are better able to absorb copper than other breeds.

Copper deficiency can be diagnosed by clinical signs, by blood tests or by liver biopsy. Serum copper levels should be above 7.5mol/l or plasma levels above 9.5mol/l. Liver biopsy is probably the most accurate indicator of copper status but it is not a very common procedure. Dietary analysis should also be carried out to look at the ratios between copper, molybdenum, iron and sulphur.

Dietary copper requirements are 10mg to 20mg/kg DM. It is also worth noting that cattle are also prone to copper toxicity, where the diet is supplemented with too much copper. This is much more likely to occur in sheep but also occurs in cattle.

Iodine

Iodine is necessary in the body for the synthesis of thyroid hormones, which are essential in regulating energy metabolism. The demand for thyroid hormone is markedly increased (2.5-fold) in high-producing cows and also in cold weather, where it is needed to increase the metabolic rate to keep the animal warm.

Symptoms of iodine deficiency include enlarged thyroid gland (goitre), hairless calves, early embryonic death, abortion, stillbirths, birth of weak calves (weak calf syndrome) and reduction of expression of heat.

Like copper, a deficiency may be primary or secondary. A primary deficiency arises where the soil is low in iodine. This is then reflected in the herbage.

Secondary deficiencies where goitregens occur in the feed. These are compounds that interfere with the formation of thyroid hormones and cause hypothyroidism. These are present in feeds such as kale, rape, beet pulp and cabbages. Nitrogen fertilisers also lower the iodine content of grasses.

In areas of marginal iodine status, the pregnant cow’s thyroid gland becomes very efficient at removing the available iodine from the plasma, which leaves very little for the foetus and this is why many of the symptoms of a deficiency are seen in the foetus.

The iodine requirement of the diet is 0.2mg/kg DM. Diagnosis of iodine deficiency can be made by clinical signs, eg. enlarged thyroid gland in stillbirth calf, by blood thyroxine levels or by blood plasma inorganic iodine (PII) measurement.

The PII blood test is probably the most commonly used and this is a measure of the very recent iodine intake by the animal.

Selenium

Selenium plays a very important role in the body as an antioxidant. In this way, it protects cell membranes from damage, and this is especially important in the period around calving (periparturient period).

It also plays an important part in the proper functioning of the immune system. In these roles, it is inextricably linked with vitamin E. Selenium deficiency during the pregnancy will result in problems with retained foetal membranes (RFM), problems with uterine health and mastitis.

Other symptoms of selenium deficiency are white-muscle disease where animals are very stiff or can die suddenly, and marginal deficiency can result in poor growth rates and general unthriftiness.

Some parts of Ireland have soils of high selenium levels and are, thus, prone to selenium toxicity. This can be acute or chronic. Acute toxicity leading to death can also occur where young cattle are injected with selenium.

Selenium nutrient requirements are 0.1mg to 0.3mg/kg DM.

Diagnosis of selenium deficiency is based on a blood test for glutathione peroxidase (GSHpx), which is an enzyme. This measures the selenium intake from up to six weeks ago.

Cobalt

Cobalt is required in the formation of vitamin B12 in the rumen. The rumen microbes can produce all the vitamin B12 required by the cow, provided sufficient cobalt is present in the diet.

Adult cattle generally have enough stores of vitamin B12 in the liver to last several months of a cobalt deficient diet, so it is in young animals that symptoms of cobalt deficiency are generally seen.

These signs include failure to grow, unthriftiness and loss of weight. More severe signs in the presence of a prolonged deficiency are anaemia with pale mucous membranes, and reduced resistance to infection.

Although the cow has sufficient reserves to withstand the prolonged deficiency, the rumen microbes do not and within a few days of being fed cobalt sufficient diet, there is a shift in the microbe population of the rumen which affects the cow’s digestion.

Cattle require 0.11mg/kg of dietary dry matter (DM) of cobalt per day. Diagnosis of cobalt deficiency is difficult as there is no accurate blood test. The appearance of a chemical called MMA in the urine can be taken to indicate a deficiency but this is not a proven test. Probably, the best way to diagnose a problem is by liver biopsy or a sample of liver from an animal sent to the factory.

Zinc

Zinc plays a big role in the function of many enzymes. Many of the effects of deficiency are seen on the skin or skeleton. Because of its role in keratin production, it may affect the teat’s natural defence mechanisms and make the cow more prone to mastitis.

Chronic deficiency will also result in poor hoof condition with resultant lameness problems.

Manganese

Most of the manganese in the body is found in the skelton, liver and hair. Deficiency symptoms include skeletal abnormalities in utero and staggering (ataxia) in newborn calves if deficiency occurred during pregnancy.

Molybdenum

Molybdenum is a component in many enzymes. Molybdenum deficiency is almost unheard of, but molybdenum excess is a far bigger problem because of its antagonism to copper.

*Donal Murphy is a partner in Sliabh Luachra Veterinary Centre, Rathmore, Co Kerry, which is a member practice of XLVets. XLVets is a group of progressive practices who work together to achieve a better future for agriculture and veterinary in Ireland. Visit www.xlvets.ie for moreinformation. This article was originally published in April 2012.

Read parts two and three of our trace elements series this Sunday