Effect of Chinese parsley Coriandrum sativum and chitosan on inhibiting the accumulation of cadmium in cultured rainbow trout Oncorhynchus mykiss

Abstract

Toxic heavy metals such as cadmium (Cd) accuulate in cultured fish from solid-form feed mixtures. In this paper, two natural ingredients, supposed to inhibit accumulation of heavy metals in the fish body, were investigated to develop a functional feed mixture for healthy fish. Three test diets: (i) #1, regular diet as negative control; (ii) #2, #1 +2% lyophilized Chinese parsley Coriandrum sativum (CP); and (iii) #3, #1 +3% chitosan (CT), were each fed to 50 rainbow trout Oncorhynchus mykiss once a day, at the constantrate of 1.0–1.2% of body weight for 12 weeks. No undesirable effect on fish growth was observed by an addition of either CP or CT to regular feed. Then, 10 mg Cd was added to 1 kg each of the three test diets and they were named as: (i) #4, #1 +Cd; (ii) #5, #2 +Cd; and (iii) #6, #3 +Cd, respectively. The fish given positive a control feed (diet #4) for 3 weeks accumulated Cd in the liver and kidney at approximately 0.52 mg/kg. However, Cd in ordinary muscle was found to be just above the detection limit. Upon accumulation of Cd, three groups of 50 fish were each fed test diets #4, #5, and #6 for 12 weeks at the same feed rate described above. The concentrations of Cd accumulated in the liver, kidney, and ordinary muscle of the fish were measured every 3 weeks. Contrary to the positive control fish fed diet #4, those fish fed test diets #5 and #6 accumulated 20–30% and 25–40% less Cd in the liver, respectively. Test diets were a little less effective for inhibition of Cd uptake in the kidney than that observed in the liver. These results suggest that addition of CP or CT to fish feed might be used to decrease toxic heavy metal accumulation in fish.