I have not written many equine science posts recently. I thought I would write a post on selenium and the problems deficiency and excess cause. This is not usually a problem unless you live in certain areas of the world. Last year we had to chose a mineral to write an essay on and I chose this because it causes lots of different effects.
Selenium acts as a biological antioxidant and prevents cell damage. It is thought that horses need around 1.00 mg of selenium a day which is a very small amounts.
A deficiency of selenium in the horse can lead to a number of problems and is often worse than in other livestock species.
The importance of selenium is highlighted as there are many conditions that horses experience than can be treated with selenium and vitamin E therapy such as myositis and azoturia.Other studies have found it could help with conditions such as infertility, muscular weakness in foals and performance problems during exercise.
White muscle disease is also called nutirional myodegeneration and is a disease caused be deficiency of vitamin E and selenium. It may be seen in foals due to a mare being deficient during pregnancy and it is more common in foals than older horses. It is a severe disease and causes weakness, stiffness and a weak suckle reflex. In severe forms they will lye down and it can cause sudden death. It can cause the muscle to turn a pale colour which gives it the name "white muscle disease". Treatments of supportive therapies can be given and supplements of selenium and vitamin E.
Exertional rhabdomyolysis is a condition that often happens after exercise and causes the horse's muscles to seem dysfunctional. This is also thought to be due to selenium deficiency. Selenium supplements are therefore given and trainers have reported it to reduce the rates of rhabdomyolysis. However, selenium may not be the primary cause of this.
Selenium has also been found to effect fertility rates in horses. It has been found to increase fertility in mares. Selenium is also associated with improved sperm quality and fertility in the stallion.
Too high levels of selenium can cause it to be toxic. An extreme example of toxicity can be seen by an event in America where 21 polo ponies died. They all collapsed and died before a competition and it was found they have very high selenium levels
Animals eating forage that is high in selenium can suffer from alkali disease. Affected animals suffer from hair loss from the manes and tails and hoof problems.
Here are the references I used for this essay just in a short form: Aleman 2007; NRC 2007; Koller and Exon 1986; Aleman 2007; Ishii et al 2002; Bertelsmann et al 2010; Aleman 2007; McGowan et al 2002; Ishii et al 2002; Bertelsmann et al 2010; Holt 2009; Tinggi 2010; Oldfield 2002.
Hope this little summary was interesting. It is strange how something needed in such small amounts can cause such severe problems if horses are deficient or in excess.