Changes in blood levels of zinc, copper, selenium, glutathione peroxidase, vitamin B12 and total and free thyroxine in sheep removed from pasture and held without food for 50 hours

Abstract

Blood was collected from a group of ten sheep immediately after removal from pasture and thereafter at regular intervals for 50 hours whilst maintaining them without food but with adequate water. The samples were analysed for parameters normally examined as an aid to the diagnosis of zinc, copper, selenium, cobalt and iodine status. Serum vitamin B₁₂ levels increased with time. Mean plasma zinc concentrations and mean serum concentrations of both T₄ and fT₄ followed significant parabolic trends. Maximum mean zinc levels (50 ± 10% higher than initial values) were recorded after 30 hours. T₄ and fT₄ levels peaked at approximately 26 hours. Zinc levels at two hours were 20 ± 5% lower than the initial values. Whole blood copper, selenium and glutathione peroxidase levels did not change significantly with time. the largest differences were 11 ± 6%, 5 ± 4% and 10 ± 8% respectively.