INFLUENCE OF DIETARY COPPER, MOLYBDENUM AND SULFUR ON COPPER METABOLISM OF SHEEP

Abstract

Twenty-eight ram lambs were allotted to one of four treatment diets on the basis of body weight (34.7 ± 6.6 kg) in a split-plot design. The pelleted diet of alfalfa-bromegrass hay (31.2%), barley (63.2%) and molasses and premix (5.6%) was fed ad libitum and contained 11.5 mg copper (Cu), 2.8 mg molybdenum (Mo) and 1.8 g sulfur (S) kg−1 (dry matter) DM. The four experimental diets were: basal (diet I); basal plus 10 mg Mo and 2 g S (diet II); basal plus 10 mg Cu, 10 mg Mo and 2 g S (diet III); basal plus 20 mg Cu, 10 mg Mo and 2 g S (diet IV), per kilogram of diet DM. Copper as copper sulfate (CuSO4∙5H2O), S as anhydrous sodium sulfate (Na2SO4) and Mo as ammonium molybdate ((NH4)6Mo7O24∙4H2O) were added and provided Cu:Mo ratio of 5.0, 0.7, 1.5 and 2.0 for diets I, II, III and IV, respectively. Lambs were fed the experimental diets in confinement for 16 wk. Measurement of body weight and samples of liver tissue and blood serum were obtained every 4 wk. The treatment diets had no significant (P > 0.05) effect on body weight. Liver Cu concentration increased for the I and IV diets and declined for II and III diets (P < 0.01). Lambs on diet II had the highest (P < 0.01) concentration of serum total Cu, Mo and trichloroacetic acid (TCA) insoluble Cu relative to lambs consuming the other diets. Lambs assigned to diet I had higher (P < 0.01) serum ceruloplasmin (Cp) activity and TCA-soluble Cu levels than lambs consuming supplemented diets. Therefore, a dietary concentration of 3.3 g kg−1 S and Cu:Mo ratio of 0.7 caused high serum Cu and TCA-insoluble Cu which did not contribute to hepatic Cu reserves. Increasing the Cu:Mo ratio in the diet reversed these effects. Key words: Copper, molybdenum, sulfur, interaction, sheep