Direct and indirect assessment of selenium status in sheep – a comparison

The aim of this study was to determine the relationship between selenium concentration and activity of glutathione peroxidase (GSH-Px) in the whole blood of sheep and reference ranges for the activity of GSH-Px for evaluation of the selenium status of sheep in the Czech Republic. Selenium concentration and activity of glutathione peroxidase were determined in whole blood samples collected from 92 sheep in six herds. The GSH-Px activity in the samples was measured using the photometric method. Selenium in the sample was measured using the hydride technique atomic absorption spectrometry. Data on both parameters were processed using correlation and regression analysis in order to obtain reference values of GSH-Px for the indirect evaluation of the selenium status of sheep. The two variables showed a close and significant correlation (r = 0.95; P < 0.01). The regression line, defined by the equation y = 7.5857x – 121.87 (linear) or y = –0.0167x2 + 11.993x – 355.57 (polynomial), allowed us to determine the GSH-Px activity of 637, resp. 677 μkat/l as equivalent to selenium concentration in whole blood of sheep 100 μg/l. Mean selenium concentration and mean GSH-Px activity found in whole blood samples were 123.42 ± 57.84 μg/l and 814.34 ± 463.64 μkat/l, respectively. In this study, a close dependence of GSH-Px activity on the selenium concentration in the blood of sheep was found. Activity values of GSH-Px were determined for use in the diagnosis of sufficient selenium status in sheep in the Czech Republic (GSH-Px activity greater than 600 μkat/l of whole blood).