Assessment of selenium status in horses -: new aspects

Selenium concentration in plasma and the activity of glutathione peroxidase in blood (GSH-Px) were measured in a total of 304 horses, aged four months to 29 years. In addition the frequent use to transform GSH-Px activity in selenium content was evaluated. GSH-Px activity in blood was analyzed by photometry and plasma selenium concentration was determined by atomic absorption spectroscopy. GSH-Px activity extended from 2 to 190 U/g Hb and plasma selenium concentration ranged from 16 to 291 mu g/l. The relationship between GSH-Px activity in blood and plasma selenium concentration is best described by the linear regression equation y = 0.78 x + 43.1, in spite of significance the correlation coefficient of r = 0.49 is rather low. It is concluded that GSH-Px activity in blood and selenium concentration in plasma should be regarded separately to assess selenium status and the transformation from GSH-Px activity in selenium content has a limited value. There is a high variability within the herd levels even if the horses were maintained under the same feeding and management conditions. The check of one horse to assess selenium status for the complete herd is of poor expressiveness.