Effects of fish oil under different stored conditions on growth performance and antioxidant indexes in juvenile grouper (Epinephelus coioides)

In order to study the effects of fish oil under different stored conditions on growth performance and antioxidant indexes in juvenile grouper, Epinephelus coioides. The conditions which the fish oil was oxidized are as follows:stored temperature:4℃, ambient temperature(AT):(31.5±3.5)℃; stored time:45, 90,135 d; supplementations of antioxidant:30 mg/Kg(EQ), 300 mg/Kg(HEQ). According to the different treatment conditions of fish oil, there were 14 groups:T_F+EQpositive control (fresh oil+ EQ), T_Fnegative control (fresh oil), T_4℃+45d+EQ, T_4℃+45d+HEQ, T_4℃+90d+EQ, T_4℃+90d+HEQ, T_4℃+135d+EQ, T_{4℃+135d+HEQ}, T_AT+45d+EQ, T_AT+45d+HEQ, T_AT+90d+EQ, T_AT+90d+HEQ, T_AT+135d+EQ, T_AT+135d+HEQ. Preparation of nitrogen and other fat diets fed the Epinephelus coioides, which is from juvenile grouper (18±0.02) g to 56 days. There were no significant differences between T_F+EQ and T_4℃+45d+EQ, but T_4℃+45d+EQ was significantly higher than T_AT+135d+EQ in WGR. The FCR of T_4℃+45d+EQ, T_4℃+45d+HEQ, T_AT+45d+EQ and T_AT+45d+HEQ were relatively low, which had no significant differences with T_F+EQ and T_F but significantly lower than T_AT+135d+EQ and T_AT+135d+HEQ (P<0.05). The cell structures of T_F+EQ, T_4℃+45d+HEQ were clear and obvious and the sizes of these fat droplets in cells were normal, but much more greater fat droplets in T_AT+135d+EQ and T_AT+135d+HEQ. The CAT of T_4℃+135d+EQ, T_AT+135d+EQ and T_AT+135d+HEQ were significantly higher than T_F+EQ and T_F. The SOD and GSH-Px were highest inT_AT+135d+EQ, which were significantly higher than T_F+EQ and T_F. The MDA of T_F+EQ, T_F, T_4℃+45d+EQ, T_4℃+45d+HEQ, T_AT+45d+EQ and T_AT+45d+HEQ in liver had no significant differences, but were significantly lower than the other groups. We found the growth performance and antioxidant index in juvenile grouper of T_4℃+45d+EQ, T_4℃+45d+HEQ, T_AT+45d+EQ and T_AT+45d+HEQ were relatively good, T_4℃+45d+EQ, T_4℃+45d+HEQ were better than T_AT+45d+EQ and T_AT+45d+HEQ. That shows short term storage, adding antioxidants are advantageous to storage of fish oil, besides 4℃ is better than ambient temperature.