Magnesium interrelationships in monogastric and ruminant animals

Seventy-two albino rats, 5 sheep and 51 bovine blood samples were utilized in this study to investigate the relationship of dietary magnesium, potassium and nitrogen on hypomagnesemia. The rats were allotted to 12 synthetic diets composed of 9, 18 and 36% casein; 0.0, 0.6 and 1.3 g/kg ration of magnesium; and 0.0, 4.0 and 8.0 g/kg potassium ration reduced magnesium levels in plasma and tissues. An interaction between dietary potassium and magnesium appeared to be present. Four wethers were fed magnesium chloride, oxide, sulfate and nitrate to study the possibility of an interaction of these compounds with body minerals. Administration of each salt increased the plasma magnesium level and fecal and urinary excretion, but resulted in a negative balance of potassium and calcium. Dosing with citric acid and trans-aconitic acid had no apparent effect upon hypomagnesemia. Intravenously administered ²⁸Mg disappeared rapidly from the blood of sheep, and after two hours was followed by a slower expotential disappearance to 20 hours. Bovine blood samples were submitted by practicing Tennessee Veterinarians from cows which died of field cases of tetany. Sample analyses were compared with that from young and old cattle from the University of Tennessee Experimental Station herds during "grass tetany" season. Analyses indicated a lower than "normal" magnesium and calcium levels for Tennessee cattle.