Dietary copper requirements of juvenile large yellow croaker Larimichthys croceus

Abstract

A 10-week feeding trial was conducted to estimate the requirement of dietary copper for juvenile large yellow croaker Larimichthys croceus (initial body weight, 9.18 ± 0.06 g). Six graded levels of dietary copper were designed as 2.61, 3.25, 4.65, 7.16, 11.38, and 18.45 mg kg− 1, respectively. Results showed that fish fed the basal diet with 2.61 mg kg− 1 of copper had the significantly lowest weight gain rate (WGR), activity of copper-zinc superoxide dismutase (Cu-Zn SOD), the total antioxidant capacity (T-AOC), the whole-body Cu concentration and the vertebrae Cu concentration (P < 0.05). When dietary copper increased from 2.61 to 4.65 mg kg− 1, the WGR significantly increased (P < 0.05). Higher dietary copper contents did not result in further increasing of WGR. Higher (> 7.16 mg kg− 1) dietary copper content significantly decreased the Cu-Zn SOD activity and T-AOC in liver (P < 0.05). No significant differences were found in survival, feed efficiency, body compositions, hepatosomatic index, viscerosomatic index and condition factor among the all treatments (P > 0.05). Based on the WGR, the optimal dietary copper content for large yellow croaker was estimated to be 3.41 mg kg− 1. Based on the whole-body Cu concentration, the vertebrae Cu concentration and the Cu-Zn SOD activity in serum, the minimum dietary copper content was estimated to be 5.30, 5.90 and 7.05 mg kg− 1, respectively.