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This article was published in 1981
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Selenium Analyses
P.J. Healy, B.V.Sc., PhD., M.A.C.V.Sc., Veterinary Research Station, NSW Dept. of Agriculture, Glenfield
The biochemistry laboratory at VRS is now able to determine selenium concentration in tissues and blood. The laboratory is now able to offer laboratory support for investigation of selenium deficiencies in livestock.
In blood of ruminants almost all the selenium is in the enzyme 'glutathione peroxidase (GSPx)'. Most GSPx activity in ruminant blood is red cell GSPx activity. Red cells only synthesise GSPx prior to leaving the bone marrow and they have an expected life of 120 days. Therefore measurement of whole blood GSPx activity (or Se concentration) reflects the availability of Se some 2 months before sampling. There is some GSPX in serum (or plasma) and the activity of this enzyme changes more rapidly with change in Se concentration in the diet. Unfortunately the activity is very low and difficult to measure accurately.
Levels of Se in tissues and blood quoted in the literature are remarkably constant, for sheep, cattle and pigs.
| NORMAL | DEFICIENT | |
|---|---|---|
| Liver | 500 mg/g | 100 mg/g |
| Kidney | 5000 mg/g | 2500 mg/g |
| Blood | 20 mg/g | 10 mg/g |
Our limited experience with GSPx activity indicate that values less than 50 µmoles/g Hb may be indicative of selenium inadequacy.
For investigation of selenium levels in a herd or flock We suggest that between 10 and 20 heparinised blood samples be submitted for GSPx activity estimations.