Selenium deficiency

Veterinary advice should be sought before applying any treatment or vaccine.

Selenium Deficiency

Selenium (Se) deficiency occurs in horses that don't receive enough selenium in their diet. A deficiency in selenium is more likely to occur in mares and foals living in regions with low selenium content in the soil. The amount of selenium that horse's require in their diet varies by age, weight, level of training/work load, and stage/type (growing, lactating, pregnant, etc).
Se Nutritional Requirements for an average, 500 kg horse
  • Adult Pleasure horse: 1 mg/kg
  • Performance horse: 1-1.25 mg/kg
  • Stallion:
    1 mg/kg
  • Pregnant Mare:
    1 mg/kg
  • Lactating Mare: 1.25 mg/kg
  • Young, growing horse: 0.42-1.07 mg/kg
European legislation recommends that horses should not be fed more than 0.5 mg of selenium per kg of total diet on a dry matter basis (equivalent to 5 mg for a 500 kg horse).


Abnormal gait
Difficulty suckling or swallowing
Difficulty breathing
Reduced performance


  • History
  • Clinical signs
  • Physical exam
  • Sensitive fluorometric Se assay



Selenium supplements : added to horse's diet, however with the guidance of a veterinarian and after conducting an accurate diet analysis, as selenium is also toxic in levels higher than 2 mg/kg DM.


Scientific Research

General Overviews

Risk Factors

  • Horses living in selenium deficient regions.