Without an adequate selenium uptake, stock health can be severely affected.
Selenium is required for wool growth, sperm motility, embryo development and an efficient antibody response against disease. Selenium along with Vitamin E are important antioxidants, helping to prevent tissue damage. With adequate selenium levels your stock have the natural building blocks to reach their full potential.
While selenium is not required by plants, problems do arise when the dietary intake of grazing animals is below 20-50 parts per billion. Without selenium, both acute and subclinical deficiency symptoms can occur.
Acute deficiencies are easier to recognise by the severity of the symptoms. Indeed in very selenium deficient areas, stock will die.
Subclinical deficiencies are harder to detect but often manifest as: low lambing percentages, loss of embryos, increased retention of placentas in cows, poor conception rates, inability to thrive due to increased disease pressure.
If selenium is that missing block, then stock healthy improvement with supplementation can be dramatic. Some Tara Hills trials in 1983 showed lambing percentages increase from 21% to 120% with the application of pasture selenium alone.
Selenium is required in up to 100 specific selenoproteins within the animal, through the uses for only 30 of them have been determined to date. All these selenoproteins have various functions, including helping animals cope with stress (such as cold weather), long milking seasons and inadequate diet. Selenium is incorporated into some enzymes which reduce tissue damage due to peroxides and free radicals.
Occasionally the deficiency of selenium can be seen in the development of recognised acute disease symptoms, but more often the deficiency comes through in subclinical symptoms, which are harder to detect.
Some of these symptoms are:
White muscle disease – this disease, also known as muscular dystrophy, can affect lambs, calves, foals and fawns, causing them to be reluctant to move.
Infertility – selenium deficiency in stock at mating can result in a high proportion of barren ewes/cows as a result of embryonic loss 3-4 weeks after conception. Selenium is also required for sperm production and motility.
Cattle may respond to selenium with a better return to oestrus, lessened calving difficulties, and fewer retained placentas. Sheep appear more responsive to selenium-induced infertility than cattle.
III Thrift – Selenium-deficient animals will fail to maintain optimum growth rates. Both live weight gains and wool weight gains can result when the deficiency is treated. Milk production gains have been reported in dairy herds with a mean selenium concentration of less than 120 nanomoles/L.
Poor Wool Growth – Selenium is a vital compound of wool. Because wool growth occurs every day, it makes large demands on a sheep’s selenium reserves. Up to 20% of a sheep’s total selenium is concentrated in the wool.
Increased Disease Susceptibility – Selenium is required for efficient antibody response, helping to reduce sub clinical mastitis and other disease pressures.