Affiliations: Department of Animal and Range Science, North Dakota
State University, Fargo, ND 58105, USA | Grand Forks Human Nutrition Research Center, Grand
Forks, ND 58203, USA
Note: [] Address for correspondence: John Finley, United States
Department of Agriculture, ARS, GFHNRC, PO Box 9034, Grand Forks, ND 58202,
USA. Tel.: +1 701 795 8486; Fax: +1 701 795 8220; E-mail:
jfinley@gfhnrc.ars.usda.gov
Abstract: It was previously reported that pigs marginally deficient in
magnesium (Mg) and fed diets high in manganese (Mn) died suddenly with signs of
sudden cardiac death. Manganese, which has properties similar to Mg, may
exacerbate Mg-deficiency and be accumulated by mitochondria resulting in
ultrastructural damage. The objective of this study was to determine whether
deaths of the type previously observed were mediated by adverse interactions of
Mn and Mg resulting in ultrastructural damage to the myocardium, alterations in
electrocardiographic recordings and tissue retention of Mn, Mg and calcium
(Ca). Forty-eight pigs were fed one of six diets in a 2 X 3 factorial
arrangement of Mg (100 or 1000 mg Mg/kg) and Mn (5, 50 or 500 mg Mn/kg) for 8
weeks. Left ventricle muscle samples were collected for examination by
transmission electron microscopy. No differences in heart muscle ultrastructure
were observed between pigs fed low and adequate dietary Mg. However, marked
myocardial necrosis and mitochondrial swelling were observed in pigs fed high
dietary Mn when combined with low Mg. Feeding low dietary Mg elevated minimum
(P < 0.01), maximum (P < 0.05) and average (P < 0.001) heart rates.
Low dietary Mg resulted in a 55% probability of a ventricular beat being
recorded (P = 0.05) and lower Mg (P < 0.02) and Ca (P < 0.04) contents in
heart atria and ventricles. These results suggest that high Mn, when fed in
combination with low Mg, disrupts mitochondrial ultrastructure and is
associated with the sudden deaths previously reported.
