Selenium has a very important role in the body, which is to protect against free-radical damage and support optimum immune function. Selenium deficiency will cause ill-thrift and poor growth in calves and lambs.
Young lambs, calves and deer can also be affected by white muscle disease which is characterised by severe muscle damage and often death. Some research has also shown selenium deficiency to cause early embryonic loss in ewes and reduced milk production and infertility in cattle.
What causes selenium deficiency?
Animal selenium levels are determined by the amount of selenium in their diet (and hence plant and soil levels). There are very few interfering minerals that prevent absorption as in the case of copper. High sulphate levels have been shown to reduce selenium absorption to some degree. Legumes tend to be lower in selenium than grasses and more alkaline soils encourage greater selenium uptake. Selenium deficiency is linked to soil type, with soils in the Horowhenua and coastal parts of the Rangitikei and Manawatu often being quite deficient.
When are selenium levels lowest?
Selenium levels in animals tend to be lowest during periods of rapid pasture growth. Selenium deficiency could become more of a problem with improved pastures. Animals do not store selenium in the body in large amounts so a regular dietary intake is important.
What is the best way of testing selenium levels?
Selenium levels can be accurately tested using liver or blood samples. Cattle are often tested in the late autumn. Five to six month-old lambs are usually the best group on which to assess selenium status on sheep farms. Pasture and soil samples can also be very useful, especially if the farm consists of more than one soil/terrain type.
The optimum time and type of test will vary between properties. Talk to Totally Vets about what is best for your farm.
