Abstract
The concentration of selenium (Se) in liver, whole blood, erythrocytes and plasma, and the activity of glutathione peroxidase (GSH-px) in erythrocytes and plasma were monitored in calves transferred between low Se and high Se pastures to determine how each test responded to changes in dietary selenium concentration.
Liver and plasma Se concentration and plasma GSH-px activity responded more rapidly than Se concentration in blood or erythrocytes and GSH-px activity in erythrocytes to changes in dietary Se intake. Erythrocyte GSH-px activity showed the greatest relative change in value.
There was a close relationship (r = 0.97) between blood Se concentration and erythrocyte GSH-px activity in samples tested from 50 mixed aged cattle.
It was concluded that Se concentrations in plasma and liver provide the best indication of current dietary Se intake in cattle, but that erythrocyte GSH-px activity provides a suitable alternative test for the diagnosis of Se deficiency and might help to define more precisely which animals are likely to respond to Se supplementation.