How to prevent selenium deficiency
There are three main ways in which selenium can be supplemented. Advice from your local veterinarian and agronomist should be sought as each case and farming system are different.
Selenium applied to pasture
Selenium concentration of pasture is increased following the application of 10 grams selenium per hectare as either sodium selenate or barium selenate.
Application of selenium in fertiliser has become widely accepted as a cost-effective way of meeting selenium needs of high stocking rate dairy, sheep and beef farmers. Frequency of application is influenced by soil type, dry matter yield of forage growth, rainfall or irrigation and the selenium requirements of the different stock classes.
Incorporation into the soil, uptake by the plant and intake by the animal may take several seasons, with slow-release barium selenate offering a more prolonged release of selenium compared with sodium selenate.
Selenium supplied as drenches, injections or pour-ons
Drenching, injections (via subcutaneous injection) and pour-on methods of selenium supplementation are available. Injections containing barium selenate as their main active ingredient have been found to provide cattle with up to 12 months’ effective selenium levels in blood.
Selenised lick blocks and loose licks
Selenised lick blocks and loose licks are also available but, due to variable consumption of these products by animals within a group, blocks and licks cannot ensure adequate levels of selenium are delivered.
Intra-ruminal selenium pellets
Intra-ruminal selenium pellets are an effective method to address selenium deficiency in cattle.
Selenium toxicity
Selenium is one of the most toxic of the trace elements. Cases of toxicity in cattle can be due to overdosing of selenium supplements, providing more than one selenium-containing supplement at the same time when animals already have high levels from their environment.
Clinical signs of selenium toxicity include:
- breathing and respiratory distress
- anorexia and weight loss
- diarrhoea
- fast heart beat
- increased incidence of urination
- sudden death.
Daily intakes of greater than 0.25 milligrams selenium per kilogram, a single oral dose of greater than 10mg Se/kg or a single injection of greater than 1.2mg Se/kg bodyweight are toxic for cattle.
Always obtain advice from your local veterinarian before deciding on a supplementation program of selenium for your livestock.
More information
For more information on selenium deficiency, contact your local veterinarian or a Department of Primary Industries and Regional Development, Western Australia (DPIRD) field veterinary officer.
The Livestock Biosecurity program contacts webpage lists DPIRD field veterinary officers in each region.