Red sea bream, Chrysophrys major, were kept on diets containing 11% of fresh (POV 5) or oxidized pollack residual oil (POV 1, 550) for 40 days.
After 20 days of feeding, the digestibility of fat was measured on 20 fish. The rest of the fish were kept for another 20 days on the experimental diets. After 2, 6, 24, 48 and 72 hours following the last feeding, the fish were sacrificed for the measurement of chemical components in the plasma and hepatopancreas.
The digestibility of the fresh oil was 91%, whereas that of the oxidized oil was as low as 77%.
Hyperglycemia was observed in 2 to 24 hours following the administration of the oxidized oil, but elevation of blood glucose level was not significant in fish fed the fresh oil. Intake of the fresh oil was followed by a rise of triglyceride level in the plasma 2 to 6 hours later, but in the case of the oxidized oil its level remained almost unchanged.
Fat content of the hepatopancreas of fish fed the oxidized oil decreased sharply between 2 and 6 hours and then showed a tendency to increase. The administration of the oxidized oil induced remarkable decrease of glycogen in the hepatopancreas.