Selenium concentrations in tissues of sheep given a subcutaneous injection of barium selenate or sodium selenate

Abstract

Young sheep were allocated to 6 treatment groups, each of 8 ewes and 8 wethers. Treatments given were nil, 0.1, or 0.5 mg selenium (Se)/kg body weight as a subcutaneous injection of sodium selenate (Na2SeO4), and 0.8, 1.4, or 2.9 mg Se/kg body weight as a subcutaneous injection of barium selenate (BaSeO4). At 14, 28, 56, and 112 days after treatment, 2 ewes and 2 wethers from each group were slaughtered and samples of blood, liver, kidney, cardiac and skeletal muscle, lymph nodes, and faeces were collected for Se assay. On days 0, 1, 3, 7, 13, 27, and 55 blood and spot faecal samples were taken for Se assay from the 24 sheep selected for slaughter on day 112. In sheep given Na2Se04 there was a rapid but transient increase in the mean Se concentration in tissues, particularly the liver of sheep given the highest dose of Na2SeO4. In these sheep on days 14,28,56, and 112 the respective mean liver concentrations were 169, 62,25, and 6.9 ¦mol/kg DM: the mean value on day 14 was 15 times the mean value in untreated sheep. In sheep given BaSeO4 there was a gradual increase in mean Se concentration of tissues during the experiment. Faecal Se concentrations increased in sheep given the Se injections. The marked but transient increase in liver Se concentrations in sheep given Na2SeO4 suggests that this organ provides an important protective mechanism against toxicity by readily accumulating and excreting Se into the gut. Our results indicate that the BaSeO4 doses were unlikely to cause Se toxicity in young sheep or result in Se residues in tissues above those recommended for human consumption. The BaSeO4 should be administered subcutaneously in the neck or other sites of the body not sold for human consumption, since deposits of BaSeO4 remain at the site of injection for at least 112 days and may be dangerous if inadvertently consumed.