Sponsored editorial from Yara

A survey in 2000 by Rothamsted Research revealed that many UK soils are deficient in Selenium, and thus producing grass that is unable to supply grazing animals with enough Selenium for optimal health. Whether this is sheep, beef, or dairy cows health effects will be seen with selenium deficient diets.

This soil survey was supported by a forage survey conducted in 2003 by Yara UK, which revealed further evidence of deficiency, with 74% of samples falling below 0.1 mg/kg DM.

At this level the grazing animal is likely to have sub-optimal blood Se levels and hence reduced Glutathione peroxidase activity. The latter being the Selenium-based enzyme that is important in detoxifying the harmful by products of normal metabolism.

Addressing this problem has been the centre of research worldwide, with the majority focusing on feed supplementation in the form of inorganic selenate added to the ration, or free access mineral licks in the grazed pasture.

Yara UK has looked at another approach – through grass fertilization. This work has demonstrated that applications of Selenium-enriched fertilizer (Top Stock) through the grazing season increased Se levels in the forage above the 0.1mg/kgDM level, subsequently raising the Se Blood levels in all cases.

This was supported further by a farm using Top Stock in 2005. As in previous work the majority of animals had greatly improved activity of the Glutathione peroxidase enzyme (Selenium based)

One distinct advantage with this approach, especially in grazing animals, is it removes the unpredictability of using free access licks. Having enriched grass ensures that during grazing all animals are receiving supplementation.

Another key aspect is that this method supplies all the selenium in the organic form, bound into seleno proteins (Se-Cysteine, and Se-Methionin), which are more readily available to the animal. The plant does the process of converting inorganic selenate into organic Selenium.