Changes in plasma and milk tocopherol levels in beef cattle turned out to pasture

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Abstract
SUMMARY Changes in tocopherol concentrations in the milk of Shorthorn cows, and blood of their calves associated with a change from a winter diet of hay to lush spring pasture were examined. During the winter feeding period the tocopherol levels in the colostrum (108 μg/100 ml) and milk (40 μg/100 ml) were low. A significant increase occurred in the milk tocopherol concentrations after the cows were turned out to spring pasture. Immediately before the animals were turned out to pasture the tocopherol levels were lower in calves with high serum levels of glutamic oxalacetic transaminase, indicative of muscular dystrophy. Plasma tocopherol levels in all calves increased throughout the grazing period, reaching a maximum average value of 919 μg tocopherol/100 ml after 63 days. Six Limousin × Shorthorn calves out of a total of 41 died with nutritional muscular dystrophy but no mortalities occurred among 26 purebred Shorthorn calves.