Effect of different dissolved oxygen levels on growth, energy metabolism and oxidative stress of Mugil cephalus

To study the effects of dissolved oxygen levels on the growth, energy metabolism and oxidative stress of mullets (Mugil cephalus), we cultivated the healthy mullets at average body weight of (29.240.08) gfor 40 d in a circulating water flow control system (251)℃ at dissolved oxygen levels of (1.560.39) mgL-1, (4.130.45) mgL-1 and (7.220.46) mgL-1, respectively. The specific growth rate (SGR), LD, SOD, T-AOC, ASOR and MDA in the plasma, muscle, lung and gill were measured; the oxygen consumption rate, ammonia excretion rate and O：N ratio were also determined. The results show that the weight gain increased with increasing dissolved oxygen content; the SGR was positively correlated with dissolved oxygen content which had significant effect on the growth of mullets. The oxygen consumption rate and ammonia excretion rate were the highest at dissolved oxygen level of 7.22 mgL-1, while O：N value was the lowest. The contents of T-SOD, T-AOC and ASOR in liver were negatively correlated with SGR. It is revealed that since the increase of oxidative stress was conflict with rapid growth, the mullets will consume more energy under oxidative stress, which leads to slow growth.