Theory Involving Propionate and Vitamin B12 in the Low-Milk Fat Syndrome

A new theory to explain the low-milk fat syndrome of cows fed high-grain, low-fiber diets is proposed.This theory involves alteration of propionate metabolism caused by increased rumen propionate production coupled with a deficiency of vitamin B~2.Attempts to correct the low-milk fat problem were through administrations of vitamin B12 to cows with depressed milk-fat.Daily intramuscular or intravenous injections of cyanocobalamin, cyanocobalamin plus folic acid, B-complex vitamins, and coenzyme B12 (6 to 18 mg of each compound) failed to increase milk fat percentage.Fifty milligrams of hydroxocobalamin injected intramuscularly increased milk fat yield approximately 200 g per day.Tripling the dosage of hydroxocobalamin (150 rag) increased milk fat percentage and yield in three of seven cows receiving the treatment.Milk fat percentage from the three cows which responded were restored to 88% of normal milk fat tests.