Abstract
Yellowtails Seriola quingueradiata were fed on non-treated, 40°C-heated, and extruder-pro-cessed brown fish meals supplemented with vitamin and mineral mixtures and pollack liver oil for 30 days. Dietary α-tocopherol was also kept constant at a level of about 90mg per 100g. Their tissue 2-thiobarbituric acid (TBA) values and superoxide dismutase and glutathione peroxidase activities as well as the resistance of yellowtails to Streptococcus sp. were examined.
Between the experimental groups of fish, no differnces were observed in the growth, the tissue enzyme activities and the resistance to Streptococcus sp.; the latter results showed that fish infected with Streptococcus sp. had strong resistance with their survival rate being high regardless of the diets used. High α-tocopherol contents and low TBA values of the diets used in the present study probably resulted in the low tissue TBA values for all the fish groups. These results also suggest that the resulting protection of various tissues of yellowtails against lipid peroxidation may be as-sociated with the possible enhancement of their biological protective ability.
