EFFECTS OF DIETARY COPPER AT DIFFERENT CONCENTRATIONS ON GIBEL CARP AND CHANNEL CATFISH

Experiments were conducted for 4 weeks to investigate the effect of dietary copper at different levels on the growth, feed utilization, hematological parameters and the copper accumulation in gibel carp (Carassius auratus gibelio) CAS III initial body weight of (128.62.0) g and channel catfish (Ictalurus punctatus)initial body weight of (159.42.0) g. Seven semipurified diets were supplemented with dietary copper (CuSO45H2O) at graded levels (3.1, 7.5, 49.8, 100.5, 506.9, 965.1 and 1491.1 mg/kg diet). The results showed that feeding rate (FI) of gibel carp was not aftected by the increase in the dietary copper concentration (P0.05); in the contrast the specific growth rate (SGR) significantly decreased. The SGR reached the lowest value when dietary copper concentration was 1491.1 mg/kg (P0.05). The feed efficiency (FE) showed a similar trend to the SGR. The viscerosomatic index (VSI) and the hepatosomatic index (HSI) also significantly decreased along with the increase in the dietary copper level (P0.05), but the condition factor (CF) was not affected (P0.05). The activity of the serum glutamie-oxalacetic transaminase (GOT) was the lowest when dietary copper concentration was 7.5 mg/kg (P0.05). However, the concentration of the dietary copper did not affect hematocrit (Hct), hemoglobin (Hb), and the activities of serum glutamic-pyruvic transaminase (GPT) and copper-zinc superoxide dismutase (Cu-Zn SOD) (P0.05). As the concentration of the dietary copper increased, the copper accumulation in the liver and the fish body was significantly elevated accordingly (P0.05), but the accumulation in fish muscles was not affected (P0.05). Similarly in channel catfish the FI was not aftected by the concentration of the dietary copper rose (P0.05); the SGR showed an apparent but non-significant decrease (P0.05); the FE dropped along with the increase in the dietary copper level (P0.05); the HSI and the CF significantly decreased as well (P0.05); but the VSI was not affected by the concentration of the dietary copper (P0.05). In channel catfish, except for Hct (P0.05) the dietary copper level did not affect the activities of serum GPT, GOT, Cu-Zn SOD and Hb. The copper accumulation in channel catfish showed a similar trend to gibel carp. In conclusion, dietary copper at high concentrations could decrease the growth and feed utilization in gibel carp and channel catfish, and channel catfish could be more sensitive than gibel carp.