The protective effects of dietary zinc on dietary copper toxicity in large yellow croaker Larimichthys croceus

• High copper intake reduced growth of juvenile large yellow croaker.
• High copper intake inhibited activities of antioxidant enzymes and lipid synthetases of fish.
• High levels of dietary zinc could mitigate the adverse effect of high copper toxicity on fish performance.

A study was carried out to test the responses of juvenile large yellow croaker to dietary copper and zinc intakes. Four experimental diets (coded as: − Cu − Zn, − Cu + Zn, + Cu − Zn and + Cu + Zn) were formulated containing two levels of Cu (4 and 24 mg/kg diet) and two levels of Zn (0 and 120 mg/kg diet), and each diet was fed to fish in triplicate for 10 weeks. Fish fed with + Cu diets (+ Cu − Zn and + Cu + Zn) had lower final body weight, weight gain, superoxide dismutase, catalase, glutathione peroxidase (GPX), 6-phosphogluconate dehydrogenase, malic enzyme, isocitrate dehydrogenase and fatty acid synthase activities than fish fed with − Cu diets (− Cu − Zn and − Cu + Zn), but fish fed with + Cu diets had higher liver Cu, muscle Cu and thiobarbituric acid reactive substance (TBARS) contents, and lipoprotein lipase (LPL) activity than fish fed with − Cu diets. By contrast, fish fed with + Zn diets (+ Cu + Zn and − Cu + Zn) had greater GPX activities than fish fed with − Zn diets (+ Cu − Zn and − Cu − Zn), but fish fed with + Zn diets had lower TBARS content and LPL activity than fish fed with − Zn diets. This study indicated that high copper intake reduced growth of juvenile large yellow croaker, inhibited activities of antioxidant enzymes and lipid synthetases. The high levels of dietary zinc could mitigate the adverse effect of high copper toxicity on fish performance.Statement of relevanceThis study will be useful in developing mineral-balanced diets for intensive culture of large yellow croaker.