Selenium and Vitamin E in Sheep Diets

Selenium and Vitamin E are essential in sheep diets on Kangaroo Island, and work together to prevent and repair cell damage in the body. Deficiencies of either or both Selenium and Vitamin E can cause weaner illthrift, reduced wool production, reduced ewe fertility, reduced immune response and white muscle disease. Kangaroo Island soils are naturally deficient in Selenium whilst Vitamin E deficiency occurs mostly in weaner sheep grazing dry pastures.
Selenium is not essential for pasture growth but is taken from the soil by plants. Sheep consume selenium with the plants they eat. Vitamin E is predominantly found in green feed. Both selenium and Vitamin E are stored for a short period in the body, mainly in the liver, so a continual dietary supply of these nutrients ensures the best possible production.

On Kangaroo Island, white muscle disease or more commonly ill thrift occurs:

• in weaners in the dry months of Summer and Autumn due to Vitamin E deficiency
• in lambs in Winter-Spring due to Selenium deficiency when green feed is abundant, especially if their mothers were Selenium-deficient during pregnancy.

Rapidly growing lambs and weaner sheep are most at risk. These young animals have an increased demand for Selenium and Vitamin E for growth and have had less opportunity than adults to accumulate body reserves.
Selenium deficiency is more likely when sheep are grazed on:

• pastures grown on selenium-deficient soils (these tend to be acid soils receiving more than 410 millimetres annual rainfall)
• lush, rapidly growing pasture
• legume-dominant pasture
• paddocks that have received heavy or long-term sulphur-containing or superphosphate fertiliser applications.

Vitamin E deficiency is widespread in weaner sheep flocks on Kangaroo Island over the long, dry Summer–Autumn period when green feed is scarce. Late lambs which have grazed green feed for less than three months are more commonly affected. Deficiency is exacerbated by feeding hay and grain as reserves are depleted more rapidly on a high grain diet.

What are the signs of Selenium and/or Vitamin E deficiencies?
Signs of deficiency include:

• poor growth
• scouring
• stiff gait
• arched back
• apparent lameness
• easily knocked over in the paddock
• reluctance to move when mustered
• sudden deaths.

What are the treatments?
Selenium 
For a quick improvement when animals show visible signs of selenium deficiency, a drench or injection containing selenium is the usual treatment. For the correct dose rate and frequency of treatment for each product, please ask at the Veterinary Clinic.
Note: Take care when giving multiple selenium supplements to avoid overdosing stock. Selenium can be fatal in lambs given an oral dose of one mg of selenium per kg liveweight (10 times recommended dose) or an injection of 0.5mg/kg liveweight (5 times recommended dose), so it is important to seek dosage advice and dose accurately.
Vitamin E
Vitamin E is available at the Veterinary Clinic both as an oil and as a powder for oral administration. Drench deficient sheep with a vitamin E drench at 2000mg/sheep. This lasts about eight weeks. Severely affected sheep may require an additional dose 3-4 weeks after the first dose.
Where sheep are too weak to bring into the yard, apply a Vitamin E powder to supplementary grain in the paddock to provide 2500–4000mg of Vitamin E per sheep.
Affected sheep will improve if they are moved onto a pasture containing green feed, such as green kikuyu (400 kgs green dry matter per hectare or more). The Vitamin E in the green feed generally corrects the deficiency within a week.

How can I prevent my sheep from becoming deficient?
Selenium
The majority of properties on Kangaroo Island will produce Selenium deficiency in un-supplemented sheep. Prevention options include:

• drenching or injecting pregnant ewes with Selenium 4–6 weeks before lambing (correct dose)
• drenching or injecting lambs with Selenium at marking (correct dose)
• giving ruminal Selenium pellets orally in sheep older than 3 months (effective for 3 years)
• injecting barium selenate salts (Selovin LA) under the skin at 1ml/50kg (effective for 2 years in adult sheep)

Vitamin E
To prevent Vitamin E deficiency, give oral drenches 6–8 weeks after pasture dries off and then every eight weeks until green feed becomes available. Providing grain treated with Vitamin E is an alternative to drenching individual sheep. In Summer and Autumn, providing access to green feed such as kikuyu where possible will assist maintaining adequate levels.
 
NOTE: If you would like more information on successfully managing weaner sheep on Kangaroo Island, please ask at the Veterinary Clinic.