Metabolism of Manganese in Calves as Affected by Dietary Manganese and Intravenous or Duodenal Manganese-54 Dosing

Fifteen intact male Holstein calves averaging 101 d of age were utilized to determine the effects of dietary Mn concentration and routes of administration on its metabolism. They were fed a practical grain diet containing 23ppm Mn with 0, 100, or 1000ppm supplemental Mn (MnSO 4 ·H 2 O) for 7 d prior to intravenous or duodenal dosing with 54 Mn. Animals were killed 4h later. With added Mn there was a significant decrease in 54 Mn content of some small intestine parts. However, in most tissue, including organs, bones, intestinal tract tissues, and blood, added Mn did not have a significant effect on 54 Mn concentrations. Concentrations of 54 Mn in tissues, except in small intestine, were far higher following intravenous dosing than with duodenal dosing. This further confirms that absorption of Mn is very low. Dosing method had a sizable effect on the relative amounts of 54 Mn in different tissues. This suggests that intravenously administered Mn, at least initially, is not metabolized in the same way as that absorbed. In most tissues, unlabeled Mn was not affected greatly by supplemental Mn. This is in contrast to earlier results with very young calves and indicates that Mn metabolism changes sharply before 3 to 4 mo of calf age.