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 deficie nt in magnesium (Mg) (4.1 mmol Mg/kg) for 5 wk. All eight pigs consuming th e 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 M g and Mn on the tissue distribution of Mg and Mn. Pigs were individually fe d, for 5 wk, diets that contained: 4.1 mmol Mg/kg and 36.0 mu mol 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 a dded ultratrace minerals, or 41.1 mmol Mg/kg and 0.91 mmol Mn/kg, and ultra trace minerals. Liver and skeletal muscle Mn concentrations were significan tly elevated by increased dietary Mn. Increased dietary Mn did not affect h eart 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 mu scle and thus may be a complicating factor in the deaths observed in Mg-def icient pigs.