BRIEF COMMUNICATION: TRACE ELEMENT DEFICIENCY IN RUMINANTS VETLAB www.pathcarevetlab.co.za Introduction: Trace elements and minerals are essential components of complete rations in sheep, goats and cattle. A complex interaction exists between the trace elements [copper (Cu), iron (Fe), selenium (Se), zinc (Zn), molybdenum (Mo), cobalt (Co) and iodine (I)]. Macro-elements (minerals) [(calcium (Ca), sodium (Na), chloride (Cl), potassium (K), phosphate (PO4), magnesium (Mg), and sulphur (S)] are also involved in these interactions. In this pamphlet the elements involved in the more common problems will be discussed briefly. Before discussing the trace elements, the following should be considered: The need for trace elements is influenced by factors in the individual animal (e.g. age and production status), in the feed and/or grazing, in the water supply, the time of the year and the management. In some parts of the country the soil (and therefore the plants) will be deficient or have excess of some of the elements. It is essential for the veterinary surgeon and the farmer to be aware of what the status of macro- and micro- elements on the particular farm or in the area is. Before consideration is given to possible trace element deficiencies, optimal rations must be ensured: e.g. unlimited access to clean fresh water, sufficient energy (carbohydrates and fat) and protein (good quality feed and pasture for the age of the animal, the developmental stage and reproductive status). The correct macro- and micro-elements should be supplemented in the ration when needed. Addition of trace elements to a ration should only be considered if the projected and actual production standards for the animals have not been met. A deficiency has to be identified and proved. Optimal nutrition is judged by the body scores at weaning, before breeding, before partus and at the end of the breeding season. Macro-minerals: Calcium and phosphorous – plant leaves are usually high in calcium and low in phosphorous. Seeds have higher phosphorous and lower calcium. Low quality pasture tends to be low in phosphorous. If fed low quality hay with no seeds (grain), phosphorous should be supplemented. If corn silage or feeds with cereal grains are fed, these may be low in calcium. Sulphur – this is a major antagonist of selenium and copper. Magnesium – can be deficient in pastures. Magnesium is poorly absorbed from rations and grazing. This mineral is involved in basic cell metabolism and deficiency leads to “tetany”. Sodium chloride - ruminants need sodium chloride (salt) to remain thrifty, make economical weight gains and reproduce. Trace elements: Factors that influence the trace element concentration in plants include fresh or dried plant material, soil pH, soil texture, and the different types of plants as well as the stage at which the plants are harvested, for example: The trace elements that may play an important role in ruminants are: SELENIUM (Se): Selenium deficiency is a widespread problem in South Africa, especially along the coastal areas and on pastures. Selenium values in the body and feed is intimately linked to vitamin E. High rainfall leads to selenium deficiency in the soil and plants. Green feed and seeds are the major sources of vitamin E. Vitamin E content of plants may fall very rapidly during periods of drought. Vitamin E is poorly stored in the body and the animals must have daily intake of adequate amounts of selenium. (If there is an increase in the pH of the soil (alkaline), the uptake of selenium in the plants is increased. Increased selenium uptake is also due to poor drainage of pastures). CLINICAL SIGNS: Sheep: Selenium and vitamin E act as anti-oxidants in the body and remove free radicals produced during metabolism. The most frequent clinical sign of selenium deficiency is white muscle disease – also known as nutritional myopathy or stiff lamb disease. This is seen in lambs of 2 – 6 weeks old. It appears that stress factors (handling, shearing and parasites) may precipitate selenium deficiency. In reproduction selenium deficiency leads to reduced sperm motility in rams. In ewes, cystic ovaries with low fertility, retained placenta and foetal membranes may occur. The quality of the colostrum is also reduced. Cattle: White muscle disease can be found in suckling calves. They also show ill-thrift. In cows, reduced milk volume, reduced conception rates and retained placentas. Mastitis may also be seen. COPPER (Cu): If pasture copper levels are adequate for plant growth it will be high enough for livestock. (Excess iron (Fe), molybdenum (Mo) and sulphur (S) in the soil will reduce availability of copper to ruminants). Poor drainage of pastures will reduce copper availability to the plants. CLINICAL SIGNS: Sheep: Copper deficiency leads to wool abnormalities (steely wool and depigmentation), anaemia, scouring and ill-thrift, increased bone fragility (lower mineral content), and infertility (delay or suppression of oestrus, abortions and foetal death). Unweaned lambs develop swayback (enzootic ataxia). Goats: The main effect of copper deficiency is on the reproduction of goats where decreased conception rates, abortions, mummified foetuses and necrotic placentitis are seen. (Goats are less susceptible to copper toxicity than sheep). Cattle: Clinical signs include coat colour changes (spectacles around the eyes, grey or brownish tinge instead of black), rough coats, reduced production of milk, anaemia, scouring in calves especially when molybdenum is increased in the diet. In adult cattle sudden death, known as “falling disease” may be seen. It is important to realise that copper requirement in cattle is higher than the requirement in sheep. www.pathcarevetlab.co.za Grass (eg. perennial rye grass) Hay Legumes and herbs Mealie (corn) silage deficiencies including P, K, S, Cu, Zn and Mg. lower mineral content than in silage. higher mineral content than grass. higher in phosphorous and lower in Ca. - - - - Compiled by: Dr Lucia Lange PathCare VetLab