Plasma Thyroxine Concentrations in Grazing Sheep in Several Areas of Australia

Abstract

Plasma thyroxine concentrations were measured by radioimmunoassay in plasma samples from 691 lactating ewes in 26 areas of New South Wales, Queensland, Western Australia and Tasmania. Sheep sampled in New South Wales and Tasmania had significantly lower plasma thyroxine values (4·0 and 4·3 Ilg/100ml respectively) than those sampled in Queensland and Western Australia (5·4 and 5·3 Ilg/1OO mI respectively). However, sheep in some districts in southern Queensland also had low plasma thyroxine values.