Selenium excretion in sheep

Abstract

Factors affecting the fate of selenium (Se) in the gastro-intestinal tract and its excretion in faeces were examined in four experiments. Large quantities of Se were secreted into the anterior region of the small intestine and were absorbed from the posterior region. These processes were not affected by the infusion of arsenite or by tying off the pancreatic duct. Faecal and urinary Se excretion were increased in sheep of higher Se status; the increase in faecal excretion was evident for several weeks after a change in Se intake but was not significant because of high variability between animals; it was attributed to the release of Se when tissues were turned over as tissue Se concentration equilibrated with contemporary Se intake. The bile was a possible route for the entry of such Se into the gastro-intestinal tract, and relationships between biliary Se and whole blood and plasma Se concentrations are presented. Faecal Se excretion was more sensitive to an increase in the organic matter intake than to an increase in forage Se concentration in one experiment. It is postulated that Se excretion was increased because rumen microbial activity was stimulated by the increased nutrient intake, and this increased the quantity of dietary Se which was reduced to an unavailable form by rumen microbial action.