Comparative studies on bioavailability and tissue uptake of two intraruminally or intraperitoneally administered esters of alpha-tocopherol in sheep.

An experiment was conducted to compare the bioavailability of dl-alpha-tocopherol acetate (TA) with that of dl-alpha-tocopherol nicotinate (TN) when administered to sheep, as a single dose, either into the rumen or the peritoneal cavity. A total of 16 sheep were used in a factorial design, with 4 sheep/treatment at the interaction level. In addition, 5 sheep that received no supplemental alpha-tocopherol, were euthanatized at the end of the trial to provide base-line data for tissue alpha-tocopherol concentrations. Curves were fitted to the plasma alpha-tocopherol concentration values, taken over 180 hours after administration of the esters. Availability of TA was greater than TN, as evidenced by the significantly higher curve parameter values (P less than 0.05) and tissue concentrations (P less than 0.05). Route of administration had a marked effect on availability of TA (P less than 0.001), but not of TN.