Selenium deficiency associations with gender, breed, serum vitamin E and creatine kinase, clinical signs and diagnoses in horses of different age groups: a retrospective examination 1996-2011.

Reasons for performing study: Selenium and vitamin E deficiency have been associated with nutritional myopathy, more commonly known as white muscle disease (WMD) in horses. However, correlations between selenium concentrations and presenting clinical signs, age, breed, gender, serum vitamin E, creatine kinase (CK) and final diagnosis, have not previously been evaluated.

Objectives: To determine the number of hospitalised horses in 3 age groups that were selenium tested and the proportions of horses with categorised presenting clinical signs; the association/odds risk of final diagnosis with selenium deficiency and to examine the association between selenium status, vitamin E status and serum CK in adult horses.

Methods: Two hundred and seventy-one hospitalised horses with a selenium concentration evaluated between 1996 and 2011 were examined retrospectively. Records were examined in order to ascertain selenium and vitamin E concentrations, age, breed, gender, CK values, presenting clinical signs and final diagnosis. Data were analysed with proportions, Fisher's exact t test, odds ratios and multivariate linear regressions.

Results: Within the < 30 day old age group, 13/20 animals had low selenium concentrations. There were 18/42 horses in the 30 days to 2 years old age group with low selenium and 77/209 horses more than 2 years of age with low selenium. There was an association between low selenium and myopathy in the < 30-day-old animals (P = 0.017), all of which were classified as having WMD. No associations were identified between nutritional myopathy and selenium status in horses between 30 days and 2 years of age or in horses more than 2 years of age.

Conclusions and potential relevance: This study indicates that WMD occurs most commonly in foals < 30 days old and is associated with low selenium concentrations (7 out of 8 affected foals had blood Selenium levels < 1.26 microm/l). Low serum selenium concentrations are common in hospitalised adult horses while nutritional myopathy is rare in these animals.