Selenium

Selenium (Se) is an essential element for animals but not plants. It is required for growth and prevention of white muscle disease in lambs and calves. White muscle disease (myopathy) is a degenerative disease affecting the skeletal and cardiac muscles causing weakness and death. Selenium also plays a role in providing resistance to disease and reproductive efficiency such as fertility and reduced incidence of retained afterbirth (when all or part of the placenta is not delivered after lambing/calving).

Seasonal variation can impact selenium levels of grazing livestock, with the lowest levels occurring in spring and summer. Known selenium deficient areas have acidic soils, high rainfall (> 500ml annual rainfall) and pastures with high super phosphate application and clover dominance. The dietary requirement is 0.05 to 0.1 mg Se/Kg of sheep and cattle (table 1).

Newborns or young livestock are affected by Selenium deficiency due to their fast-paced growth and higher requirement for Selenium. White muscle disease is more common in Victoria in lambs as they have higher Selenium requirements than calves. Young stock are more affected during lush feed situations. White muscle disease in lambs and calves is more prevalent in years when there is good autumn rainfall and abundant supply of clover in spring.

Clinical Signs of selenium deficiency may include:

• Ill thrift in young cattle, sheep and goats
• Poor growth
• Reduced conception rates, especially in younger breeding heifers and ewes
• Reduced wool production
• Retained foetal membranes
• Stiff legged gait

Flocks experiencing significant cases of white muscle disease annually should administer a selenium supplement to:

• Rams and ewes prior to mating
• Ewes in mid to late pregnancy to ensure adequate selenium levels are transferred to the foetus
• Lambs at marking and weaning

Excess selenium can be toxic. For this reason, care should be taken when considering selenium supplementation of livestock and consult your veterinarian first.

Cobalt/Vitamin B12

Cobalt is essential for the production of vitamin B12 in the rumen. In plants cobalt is required in minute amounts by bacteria that fix nitrogen in legumes.

Cobalt, and therefore vitamin B12, deficiency can be seen in association with heavy application of lime and superphosphate fertilisers to pasture.

Seasonal variations in pasture cobalt levels are significant. Concentrations of cobalt in pastures and corresponding levels of vitamin B12 in livestock are lowest during the spring flush. This may be due to stock not ingesting soil when grazing lush, rapidly growing pastures. Soils provide a more concentrated source of cobalt for ruminants then pastures.

Cobalt deficiency in sheep and cattle occurs in soils measuring cobalt concentrations of less than 0.10 mg/kg dry weight (table 1). A blood test may be used to confirm deficiency but this is not widely available.

Animals deficient in cobalt and vitamin B12 may exhibit the following symptoms:

• Poor appetite
• Poor body condition
• Weeping ‘rheumy’ eyes
• Scaly ears
• Anaemia
• Decreased milk production
• Death in severe and prolonged cases

Immediate treatment for animals showing clinical signs of deficiency is a vitamin B12 injection, which may last up to 3 months depending on the level of the deficiency.

 Young, growing animals and pregnant/lactating animals have the highest requirement for vitamin B12.

Prevention and Treatment

Mineral supplementations are available as injections, capsules (boluses), drenches, pour-ons or as loose licks depending on the mineral(s) to be supplemented. They can also be applied through fertiliser additives or pasture sprays but aren’t as effective at directly treating the animal. Before starting an intensive supplement program, it is recommended you consult with your local veterinarian or ruminant nutritionist.

It is useful to know what mineral deficiencies are common for your area. This information can be found by contacting your local veterinarian or Ag Department office for regional mineral deficiency data on 136 186 or find your local office number here.