High dietary vitamin A interferes with tissue α-tocopherol concentrations in fattening pigs: a study that examines administration and withdrawal times.

This study aimed to assess the interaction between different dietary vitamin A (dVitA) levels and the same concentration of vitamin E (100 IU all-rac-α-tocopheryl acetate/kg feed) in growing-finishing pigs. In the first experiment, two fat sources × two dVitA levels (0 v. 100 000 IU) were used. The supplementation of 100 000 IU dVitA induced a range of 5.13 to 30.03 μg retinol/g liver, 62.78 to 426.88 μg retinol palmitate/g liver, and 0.60 to 1.96 μg retinol/g fat. Dietary fat did not affect retinol or retinyl palmitate deposition in pigs. The high concentration of dVitA produced lower fat and liver α-tocopherol concentrations, and increased susceptibility of muscle tissue to oxidation. A second experiment was carried out to study the retinol and α-tocopherol retention at different withdrawal times prior to slaughter (two dVitA levels; 0 v. 100 000 IU). A high dose of 100 000 IU vitamin A during a short 2-week period was enough to induce α-tocopherol depletion in liver and fat to a similar extent as when 100 000 IU were administered during the whole fattening. Muscle, fat and liver α-tocopherol concentrations were not affected by dVitA in the 1300-13 000 IU/kg range, but liver α-tocopherol concentration was higher when vitamin A was removed from the vitamin mix 5 weeks prior to slaughter (experiment 3).