METABOLISM OF SELENIUM AND COPPER IN SHEEP WITH AND WITHOUT SODIUM-BICARBONATE SUPPLEMENTATION

The interrelationship in metabolism between dietary selenium (Se) and copper (Cu) was investigated in sheep receiving a diet with or without sodium bicarbonate (NaHCO3). A sheep finishing diet, containing 0.3 m g Se/kg DM and 7.4 mg Cu/kg DM, and supplemented with 1.0 mg Se (as Na 2SeO3) and/or 15.0 mg Cu (as CuSO4) and/or 40 g NaHCO3 per kg feed, wa s fed to young ewes for a period of 64 days. Hepatic Cu concentration and net accumulation were not affected by NaHCO, supplementation. Furt hermore, no evidence was found in blood, tissues or faeces to show tha t NaHCO3 influenced Se metabolism. However, hepatic Cu concentration w as raised from 354 to 422 mg/kg DM (P < 0.05) when the diet was supple mented with 1 mg Se/kg DM, independent of the level of dietary Cu. Fur thermore, hepatic Cu retention was significantly (P < 0.05) influenced by a Se x Cu interaction, namely when the diet was supplemented with 15.0 mg CuSO4 or 1.0 mg Na2SeO3/kg DM or both, 0.084, 0.081 and 0.088 of the dietary Cu respectively was retained in the liver, compared to 0.047 in the sheep on the basal diet. In addition, supplementation wit h Se and Cu together increased hepatic Se concentration to a greater e xtent (P < 0.001) than when Se alone was added to the feed (3.65 v. 5. 17 mg Se/kg DM respectively). The concentration of Se in both muscle t issue and in rumen bacteria was raised (P < 0.001) by Se supplementati on, but more so (P < 0.05) in both cases when Cu was not added to the diet. Interactions between Se and Cu were not influenced by NaHCO3 sup plementation in the conditions of this study.