Transient lowering of plasma vitamin B-12 concentrations in Ouessant sheepfed on a potassium-rich ration

The hypothesis tested was that a high intake of potassium (K) interferes wi th cobalt (Co)-vitamin B-12 metabolism in ruminants. Ouessant sheep were fe d either a low- (8 g K/kg dry matter) or high-K diet (43 g K/kg dry matter) with an adequate amount of Co (124 mu g Co/kg dry matter). Plasma vitamin B-12 concentrations wen measured. Sheep fed a low-K diet, but containing on ly 70 mu g Co/kg dry matter, served as positive controls. Feeding the low-C o ration produced a significant decrease in plasma vitamin B-12 concentrati ons. The high- versus low-K ration induced a significant decrease in plasma vitamin B-12 during the first 6 weeks, but thereafter the values in the hi gh-K group rose to those seen in the low-K group. The mechanism by which di etary K may interact with Go-vitamin B-12 metabolism in sheep is unknown.