THE EFFECTS OF COPPER STATUS ON THIAMINE METABOLISM IN SHEEP FED A HIGH SULFUR DIET

The effect of Cu status on selected aspects of thiamine metabolism was studied in sheep exposed to high dietary S over a period of 14 wk. Nine cross-bred 2-mo-old female lambs were used. The animals were divided into three groups (n = 3) and offered a basal diet containing 0.63% S (0.45% as sulfate) and 14 mg thiamine kg-1 DM. Copper and Mo were variable ingredients. Sheep in group 1 received a 14 mg Cu kg-1 DM diet, whereas those in groups 2 and 3 received a 6 mg Cu kg-1 DM diet. To precipitate Cu insufficiency, group 3 received an additional 20 mg Mo kg-1 DM diet. The concentration of blood thiamine tended to increase in sheep from group 1, but decline in sheep from group 3 which also had a lower concentration of Cu in plasma. In these groups, a similar trend was observed in thiamine and Cu concentrations of duodenal fluid. Liver thiamine tended to be higher (P = 0.09) in group 3 sheep than in group 1 and 2 sheep. However, the concentration of thiamine in the kidney and cerebral cortex did not differ among the groups. Copper concentration was lowest in the liver and brain, but highest in the kidney of sheep from group 3. The erythrocyte thiamine pyrophosphate (TPP) effect increased (P < 0.035) in sheep in groups 2 and 3 during the 8th week on the diet and in all sheep during the 13th week. We conclude that Cu plays an important role in the metabolism of thiamine in the gastrointestinal tract, as well as systemically.