Kinetic behavior of three preparations of α-tocopherol after oral administration to postpubertal heifers
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Abstract
Objective—To assess the kinetic behavior of 3 preparations of α-tocopherol (vitamin E) after oral administration to heifers.
Animals—8 postpubertal Friesian heifers.
Procedure—A single oral bolus of 5,000 U of α-tocopherol in oil or encapsulated in liposomes or cyclodextrin was administered to each cow, using a 4 X 4 design with 8 days between treatments. Blood samples for kinetic analyses were obtained at various times for 168 hours after treatment.
Results—Mean (± SEM) maximal plasma concentrations of α-tocopherol were 4.86 ± 0.49 µg/ml, 5.03 ± 0.39 µg/ml, and 5.08 ± 0.56 µg/ml after administration of oil, liposomal, and cyclodextrin preparations, respectively. Plasma concentrations peaked 21 to 34 hours after administration. The disappearance rate constant (Kd) was less after administration of α-tocopherol encapsulated in liposomes, compared with the other 2 preparations. Area under the concentration versus time curve was greater after administration of either encapsulated form of α-tocopherol, compared with α-tocopherol in oil, but these differences were not significant.
Conclusions and Clinical Relevance—The lower Kd determined for α-tocopherol encapsulated in liposomes suggests that this formulation may result in longer persistance of the vitamin in plasma than the other 2 preparations. Dietary supplementation with α-tocopherol encapsulated in liposomes may enhance plasma availability of this vitamin in cattle and could be useful during periods of increased vitamin E requirements, such as parturition and early stages of life. (Am J Vet Res 2000;61:589–593)
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