Effects of dietary squid liver powder content on the growth performance, cadmium accumulation and nonspecific immune response of juvenile olive flounder Paralichthys olivaceus

This study was conducted to investigate the effects of dietary squid liver powder (SLP) content on the growth performance, cadmium accumulation, and non-specific immune response in juvenile olive flounder. The experimental diets included the control diet (S0) without addition of SLP and 5 different treatments which contained 3.9 % (S3.9), 12.0 % (S12.0), 20.1 % (S20.1), 36.2 % (S36.2), and 52.3 % (S52.3) dietary SLP with the final cadmium concentrations of 0.4, 0.8, 1.7, 2.5, 4.6, and 6.4 mg kg(-1) diet, respectively. For feeding trial, seven hundred twenty fish (initial weight of 55 g) were randomly distributed into six dietary groups in triplicates (40 fish per tank). At Week 1, 2, 4, 6, and 8 (the end) of the trial, 2 fish were collected from each tank for cadmium content determination. There was no significant difference in survival between all the experimental diets. Weight gain and feed efficiency of fish significantly increased in the fish fed S52.3 compared to the other treatments. Cadmium contents in the viscera including liver significantly increased as dietary SPL content goes up at all analyses from Week 1 to 8. On the contrary, the whole body excluding viscera showed no significant difference in the cadmium content between the experimental diets, and cadmium contents in the whole body were measured below 0.08 mg kg(-1) in all the experimental groups at all times of analysis during the 8 week experiment. Superoxide dismutase and lysozyme activities in the fish plasma were significantly affected by dietary SLP contents. It could be concluded that cadmium accumulation in body (excluded the viscera and liver) of juvenile olive flounder fed with SLP-containing diets up to 8 weeks does not raise an issue related to food safety.

Automated summary

The study showed that increasing dietary squid liver powder (SLP) content led to significant improvements in weight gain and feed efficiency in juvenile olive flounder, as well as an increase in cadmium accumulation in the viscera. However, the cadmium content in the whole body remained within safe levels.