Poorer grazing covers mean adequate mineral supplementation is particularly important in pregnant ewes this winter.

The mild autumn saw grass continue to grow strongly in many parts of the country, however, heavy rainfall has left many fields inaccessible. While this could increase the grazing available to ewes in the later winter or early spring, Alicia Wilson of Trouw Nutrition says grazing needs careful supplementation to optimise productivity.

“The importance of balancing energy and protein requirements, especially during mid-late gestation and early lactation is generally understood. However, to ensure optimum utilisation of the diet, trace minerals must also be balanced.”

While the major elements – calcium, phosphorus, magnesium, and sodium – are usually supplied in grass at adequate levels and require minimal supplementation to meet requirements, Mrs Wilson stressed that the same is not true for the essential trace minerals.

“Crucial minerals including selenium, iodine, cobalt, and zinc are found in low quantities in grass, particularly in over-wintered swards. All trace minerals play different but essential roles and although the amounts required can be very small, the impact of shortfalls on health and productivity can be significant. So effective supplementation should be incorporated in diets for ewes,” she said adding that ewes may be deficient without showing significant clinical signs.

The consequences can include lambs with lower birth weights, lower milk yields, reduced colostrum and milk quality, and more problematic lambings. Selenium, cobalt, iodine, zinc, and manganese are all important, with selenium and vitamin E particularly important during late pregnancy.

These are vital nutrients essential for the functioning of the reproductive, muscular, and immune systems.

“The challenge when delivering responsible mineral nutrition to ewes is to balance the variation in mineral intakes, which is a direct consequence of variable feed intakes during late pregnancy and early lactation. A key factor in ensuring effective mineral supply in the source of minerals fed,” she added.

Minerals are only of value to an animal when they are absorbed across the intestinal wall into the bloodstream. Around 90% of all minerals fed to ewes are from inorganic sources such as sulphates and oxides which have very low relative bio-availability.

As inorganic minerals are largely unavailable to the animal due to stability and bio-availability limitations, the majority will not be used by the animal and therefore excreted possibly reducing the performance of both ewes and lambs. It is important to ensure mineral supplements contain minerals from more bio-available sources where possible.

Organic and hydroxy trace minerals, such as Intellibond zinc and manganese, have higher bio-availability as they do not react or break down in the rumen and feed. This ensures a steady, and consistent release of minerals throughout the digestive tract. Research shows hydroxy trace minerals are twice as bio-available as inorganic sources.

“Paying closer attention to mineral levels and the sources of those minerals can have a significant impact on ewe productivity, helping make the most of the total diet to improve lamb performance resulting in higher flock margins,” Mrs Wilson concluded.