[Vitamin E activity of stored forages and incidence of myopathy in calves].

Two experiments to study nutritional muscular dystrophy (N.M.D.) in calves were conducted in northern Ontario, where the disease is prevalent. In the first experiment, ninety Shorthorn cows were used. They were divided into three groups and fed the following forages during the winter of 1972-1973. Group I - Silage. Group II. - Heated-air-dried hay. Group III. - Field-dried hay. Chemical analysis of the forage during storage showed that the silage had a higher tocopherol content than the other two forages. This higher content had a direct effect on plasma tocopherol concentrations in the cows, since tocopherol levels were found to be higher in the group fed silage than in the other two groups. The highest mortality rate-eight dead calves-was in the group fed heated-air-dried hay; one calf died in each of the other two groups. Hence, it is evident that the severity of N.M.D. symptoms in calves is directly linked with the quantity of selenium or vitamin E ingested. The substances act synergistically to protect against the disease. In a second experiment, a herd of forty-seven Shorthorn cows, some of which had calves with N.N.D. and some of which had healthy offspring, were studied to measure the activity of serum creatine phosphokinase. The dams were found to have the same C.P.K., whether or not their calves suffered from N.M.D.