α-Tocopherol in plasma and milk from organically managed dairy cows fed natural or synthetic vitamin E or seaweed

The objective was to compare the effects of supplementing lactating dairy cows with synthetic (All-rac), natural (RRR) all-rac-alpha-tocopheryl acetate or seaweed with a control on the concentration of alpha-tocopherol in blood and milk. Twenty four dairy cows in mid lactation, fed an organic feed ration, were randomly allocated to the four treatments in a replicated Latin square design. Plasma and milk alpha-tocopherol concentrations were higher in RRR and All-rac than in the other treatments and higher in RRR than in All-rac. RRR-alpha-tocopherol was the predominant steroisomer (> 86%), in both plasma and milk, whereas the remaining part was largely made up by the three synthetic 2R isomers. In cows fed the control, seaweed and RRR, the proportion of RRR-alpha-tocopherol in plasma and milk constituted more than 97% of the total alpha-tocopherol. The study demonstrated that dairy cows in mid and late lactation have preferential uptake of RRR-alpha-tocopherol compared to other stereoisomers.