Effect of gamma irradiation on alpha-tocopherol levels in ruminant blood samples.

Quantification of circulating levels of vitamin E in free-ranging species can provide useful guidelines for evaluating nutrient status in captive exotic animals. Under current USDA regulations, ruminant plasma or serum samples must be subjected to 1) live-animal testing and viral screening, or 2) gamma (gamma-) irradiation prior to importation. Because irradiation is known to promote free radical formation and destruction of alpha-tocopherol in various tissues, these studies were conducted to evaluate the effect of irradiation on ruminant blood fractions with and without added antioxidant. alpha-tocopherol levels were measured in paired (irradiated vs. unirradiated) plasma or serum samples collected from zoo ruminants (n = 8 spp.). Irradiation caused highly significant (P less than 0.001) but inconsistent destruction of alpha-tocopherol. Addition of 10% volume of a 1% pyrogallol solution to plasma or serum protected against alpha-tocopherol deterioration during gamma-irradiation. In order to ensure valid comparative values for vitamin E studies while complying with USDA regulations, it is recommended that plasma or serum samples collected from ruminants outside the US be treated with antioxidant prior to importation.