High dietary manganese lowers heart magnesium in pigs fed a low-magnesium diet.

Young pigs were fed a diet moderately high or low in manganese (Mn) (0.95 +/- 0.10 mmol Mn/kg, n = 8 or 0.040 +/- 0.003 mmol Mn/kg, n = 6) and deficient in magnesium (Mg) (4.1 mmol Mg/kg) for 5 wk. All eight pigs consuming the high Mn diet died following convulsive seizures, whereas only two of six died in the group fed low Mn. In an attempt to determine the cause of death, a subsequent study examined the interactive effect of deficient dietary Mg and Mn on the tissue distribution of Mg and Mn. Pigs were individually fed, for 5 wk, diets that contained: 4.1 mmol Mg/kg and 36.0 micromol Mn/kg, 4.1 mmol Mg/kg and 0.91 mmol Mn/kg, 4.1 mmol Mg/kg and 0.91 mmol Mn/kg with added ultratrace minerals, or 41.1 mmol Mg/kg and 0. 91 mmol Mn/kg, and ultratrace minerals. Liver and skeletal muscle Mn concentrations were significantly elevated by increased dietary Mn. Increased dietary Mn did not affect heart Mn, but heart Mg concentrations were significantly depressed by high, as compared to low, dietary Mn (38.7 +/- 3.3 vs. 32.7 +/- 2.6 mmol Mg/kg). These data suggest high dietary Mn may exacerbate Mg deficiency in heart muscle and thus may be a complicating factor in the deaths observed in Mg-deficient pigs.