Effects of dietary copper, molybdenum and sulfur on biliary copper and zinc excretion in Simmental and Angus cattle

The effect of increased dietary copper (Cu), molybdenum (Mo) and sulfur (S) on biliary Cu and zinc (Zn) excretion was studied in four Angus and four Simmental heifers surgically prepared for bile collection. Initially, two of each breed were fed a low(L)-Cu and two a high(H)-Cu diet for 2 mo. All animals were then transferred sequentially to diets containing LCu–HS for 1.5 mo, HCu–HS for 2 mo, HCu–HMo for 2 mo and HCu–HMo–HS for 2 mo. Bile flow and biliary Cu and Zn concentration were measured on two consecutive days each month. Plasma Cu concentrations were measured once monthly. Biliary Cu concentrations (mg L −1 ) and bile Cu excretion (mg 6h −1 ) were greater (P