The excretion by sheep of 75selenium incorporated into red clover (Trifolium pratense L.): The chemical nature of the excreted selenium and its uptake by three plant species

Abstract

Data are prsented on the excretion of radioactive selenium by 2 sheep fed on red clover grown in nutrient solutions containing 75Selenite ion. The clover contained a total of 6.1 p.g of selenium, which was predominantly incorporated in protein. The major part of the radioactivity was excreted in the faeces, 53.8 per cent and 53.6 per cent being recovered within 99 hr for 2 sheep, while the corresponding urinary values were 1.78 per cent and 2.29 per cent respectively. The peak of excretion occurred approximately 20 hr after feeding, although 75Se was still being excreted 14 days after commencement of the experiment. Chemical fractionation of the dung revealed that mOlit of the 75Se was present in forms insoluble in solvents. The insoluble selenium was predominantly inorganic, although a smaller proportion was incorporated into protein. In plant nutrition experiments involving growth of 3 pasture species for 75 days in the presence of radioactive dung, less than 0.3 per cent of the added radioactivity was recovered in the herbage. The uptake of 75Se by brown-top (Agrostis tenuis Sibth.) seedlings was significantly higher on a dry weight basis than by perennial ryegrass (Lolium perenne L.) and by red clover (Trifolium pratense L.). © Taylor & Francis Group, LLC.