Influence of dietary vitamins A and E on serum α- and γ-tocopherols, retinol, retinyl palmitate and carotenoid concentrations in Humboldt penguins ( Spheniscus humboldti)

Abstract

Serum retinol, retinyl palmitate, β-carotene, cryptoxanthin, lutein, α-tocopherol and γ-tocopherol were measured in 18 captive Humboldt penguins ( Spheniscus humboldti) prior to and following the removal of Columbia River (CR) smelt ( Thaleichthys pacificus) from the diet. Dietary vitamin A was reduced from 59.8 to 13.5 IU g −1 (dry matter basis) when CR smelt was removed from the diet. Minimal changes were noted in dietary vitamin E. Serum samples Without-CR smelt had significantly lower circulating retinol (1.19±0.09 vs. 1.94±0.08 μg ml −1) and retinyl palmitate (0.033±0.012 vs. 0.105±0.004 μg ml −1) compared to samples With-CR. The Without-CR smelt diet resulted in increased serum α-tocopherol from 26.4±0.94 to 39.1±3.72 μg ml −1. More serum samples taken Without-CR smelt had detectable levels of γ-tocopherol than those With-CR smelt. Serum lutein was higher for the samples taken Without versus With-CR smelt. Serum cryptoxanthin did not differ. β-Carotene was not detected. Data indicate that high levels of dietary vitamin A can affect circulating levels of retinol, retinyl palmitate and vitamin E. Thus, dietary vitamin A and the interrelationship between vitamins A and E should be considered when assessing captive penguins.