Kinetic behavior of three preparations of alpha-tocopherol after oral administration to postpubertal heifers

Objective-To assess the kinetic behavior of 3 preparations of alpha-tocophe rol (vitamin E) after oral administration to heifers. Animals-8 postpubertal Friesian heifers, Procedure-A single oral bolus of 5,000 U of alpha-tocopherol in oil or enca psulated in liposomes or cyclodextrin was administered to each cow, using a 4 X 4 design with 8 days between treatments. Blood samples for kinetic ana lyses were obtained at various limes for 168 hours after treatment. Results-Mean (+/- SEM) maximal plasma concentrations of a-tocopherol were 4 .86 +/- 0.49 mu g/ml, 5.03 +/- 0.39 mu g/ml, and 5.08 +/- 0.56 mu g/ml afte r administration of oil, liposomal, and cyclodextrin preparations, respecti vely. Plasma concentrations peaked 21 to 34 hours after administration. The disappearance rate constant (K-d) was less after administration of alpha-t ocopherol encapsulated in liposomes, compared with the other 2 preparations . Area under the concentration versus time curve was greater after administ ration of either encapsulated form of alpha-tocopherol, compared with alpha -tocopherol in oil, but these differences were not significant. Conclusions and Clinical Relevance-The lower K-d determined for alpha-tocop herol encapsulated in liposomes suggests that this formulation may result i n longer persistance of the vitamin in plasma than the other 2 preparations . Dietary supplementation with alpha-tocopherol encapsulated in liposomes m ay enhance plasma availability of this vitamin in cattle and could be usefu l during periods of increased vitamin E requirements, such as parturition a nd early stages of life.