The absorption of dietary manganese by dairy cows

Additional manganese, sufficient to increase the dietary concentration to approximately 1000 mg/kg, was administered to one cow for four and another for seven days. Manganese concentrations in portal and mesenteric plasma were increased by a mean of 3.9 microgram/litre above the concentration in systemic plasma. This increment is equivalent to the absorption of 0.54 per cent of the administered manganese. The cow which received manganese for seven days showed after six days larger increases in systemic plasma manganese concentration which may indicate a toxic effect of excess manganese upon the liver.