Low serum magnesium due to a shortage of magnesium in the diet was detected in a herd of dairy cattle. Serum biochemical values were obtained from these cows from 1970 to 1971. Fifteen of twenty lactating dairy cows became ketotic in August, 1971, accompanied by dramatic changes in the blood serum. Blood serum magnesium contents were within the limits of 1.50 to 1.88 meq/litter, during the whole year, fairly low compared to the normal ranges of 1.8 to 2.2 meq/liter. Blood serum calcium, inorganic phosphorus, and transaminase activity values fell suddenly, and then most of the cows were diagnosed as being ketotic accompanied by clinical symptoms and elevated acetone excretion in urine.
This bovine ketosis was diagnosed as caused by:
(1) disturbances in the oxidative decarboxylation reaction from α-ketoglutarate to succinyl-CoA, (accumulation of α-ketoglutarate and depression of succinyl-CoA)
(2) the shortage of succinyl-CoA brought on the accumulation of acetoacetate and another ketone bodies.
Oxidative decarboxylation reactions from pyruvate to acetyl-CoA and fromα-keto-glutarate to succinyl-CoA could be suppressed by a deficiency in one of the co-factors such as Thiamine diphosphate, Lipoate, Coenzyme A, Nicotinamide adenine dinucleotide, Flavin adenine dinucleotide, and Magnesium ion.
The mass outbreak of bovine ketosis in a certain dairy farm must be caused by the disturbances of magnesium metabolism or by the shortage of magnesium intake in the rations.