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Mineral Supplementation for Ewes and Lambs

20 December 2019
Type Media Article

By Joanne Masterson, B&T Drystock Adviser, Teagasc Galway/Clare

Mineral deficiencies in sheep flocks can affect performance, fertility and profitability of your flock. Farms in areas where it is known that there is a deficiency will routinely supplement flocks with minerals as a preventative measure. Supplementation can add extra labour and financial costs on farms and in some cases it may not be necessary. It is estimated that Irish sheep producers spend approximately €3million annually on mineral drenches and boluses. In order for you to know if you have a problem with mineral deficiencies it is important to know risk factors and signs to help you understand what mineral is lacking and what strategy to use going forward.

Firstly it is important to understand the difference between Major and Trace (minor) minerals.

Major elements include the following minerals: Calcium, Phosphorus, Sodium, Magnesium, Sulphur, Potassium and Chloride. Major elements exist in larger levels in the ewe and are required in larger amounts in the diet. In the case of grass forage major elements are well supplied in grass therefore not as much supplementation is needed in this case.

Trace minerals include: Copper, Zinc, Cobalt, Manganese, Selenium, Iodine and Iron. Trace minerals exist at low levels in the animal’s body and smaller amounts are required in the diet. Trace element levels are lower in grass so that is why more supplementation of these minerals is needed. Growing animals have the highest demand for trace minerals in particular growing lambs. They are born with low reserves stored in their body so it may be seen sooner if there is an issue.

Calcium deficiency (milk fever/hypocalcaemia)

Calcium deficiency is most commonly seen during the last 6 weeks of pregnancy and is due to the increased calcium demand in late pregnancy. Risk factors are sudden changes in diet or stress such as housing, gathering or bad weather. You may notice ewes becoming weak, staggering unable to stand and in some cases prolapse. To prevent milk fever it is important to provide adequate nutrition for pregnant ewes in particular in mid to late pregnancy by providing a balanced mineral mix in late pregnancy. Also stress should be avoided in pregnant ewes during this time.

Magnesium Deficiency (Grass Tetany)

Grass tetany can occur when there are low blood magnesium levels in the ewe’s body. It is most common during the 6 weeks following lambing. It can be a risk during times when grass is lush as this is low in magnesium and high in potassium which can have an adverse effect. Also if ewes are stressed, poor weather, malnutrition or any other underlying issues they are more likely to be at risk. The signs of grass tetany are excitability or being nervous, muscle tremors, shaking, convulsions or seizures, this is then rapidly followed by death. To prevent grass tetany observe stock when you move them into lush pastures (spring grazing), minimise stress, provide shelter and feed during bad weather, provide an adequate intake of magnesium through either concentrates, licks, or buckets.

Trace Mineral Deficiencies

Cobalt Deficiency

Cobalt is linked to its role in the production of vitamin B12 in the rumen. When we talk about cobalt deficiency it is more suitable to call it a vitamin B12 deficiency. A good strategy is to try to provide a consistent supply of cobalt to your flock as cobalt is not stored in big quantities in the ewe’s body. It can be more of an issue in growing stock. Signs of deficiency would be reduced growth rate, poor thrive (pine), dry scaly skin on the ears and face and a loss of springiness of the wool.  If it is necessary to control and prevent cobalt deficiency, supplement with cobalt in the form of bolus, feed minerals, drenching or mineral licks.

Copper Deficiency

Copper deficiency occurs when sheep are grazing pastures low in copper. Some breeds are more susceptible to copper deficiency. In general hill breeds are more susceptible to deficiency issues such as swayback, while lowland breeds such as Suffolk’s and Suffolk Crosses are more susceptible to toxicity. Signs of copper deficiency would be swayback in lambs; poor weigh gain, poor fleece (steely wool). It is also important to be aware that soil molybdenum (Mo) can interfere with copper metabolism. Excess (Mo) in pasture can bring on copper deficiency in animals. Timing and type of copper supplementation is important to avoid toxicity. Appropriate use of supplementation in particular in mid pregnancy may prevent swayback issues.

Selenium Deficiency

Selenium is important for rapidly growing young animals. In certain areas soils can be deficient in selenium. Signs that there may be an issue with selenium are if you see weak lambs being born, poor growth rates and white muscle disease (which is sudden stiffness) in rapidly growing lambs. If lambs have white muscle disease it can be treated with intramuscular or subcutaneous injection of selenium.


The annual sheep census date is the 31st December 2019. Postal returns of the census are due back by 31st January and online returns on the 14th February.