Abstract:

The feeding experiment lasted for 40 days to explore the effects of breeding density (30, 60 and 90 individuals·m^-3) on the growth, enzyme activity and mRNA expression of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) in liver and kidney of juvenile Pampus argenteus with an average body weight of (3.88±0.72) g. Results are as follows. The weight gain rate and specific growth rate of the 60 individuals·m ^-3 group were (235.19±10.23)% and (4.03±0.10)%, respectively, which were significantly higher than those in the 30 individuals·m^-3 group (p<0.05), but showed no significant differences with the 90 individuals·m^-3 group (p>0.05). The changes of enzyme activity of juvenile Pampus argenteus were the most significant in the 90 individuals·m^-3 group and were the least significant in the 30 individuals·m^-3group. The activities of LDH, ALT and AST in liver and kidney increased first and then decreased, and the values of the three enzyme activities reached the peak at 6 h, 10 d and 10 d, respectively, which were 2.0 times, 4.3 times and 2.0 times of the initial values. The peak values of the three enzyme activities appeared at 1 d, 3 d and 5 d in kidney, respectively, and the values were 2.1 times, 2.2 times and 3.1 times of the initial values. The changes of mRNA expression of AST, ALT and LDH genes and the changes of the three enzyme activities in liver and kidney showed significant correlations. In conclusion, the breeding density of 60 individuals·m^-3 could promote the growth of juvenile Pampus argenteus. However, the 90 individuals·m^-3 group might cause extra energy demand increases in Pampus argenteus juveniles. Increased expression of gluconeogenesis-related genes mRNA resulted in significant increases of AST, ALT and LDH activities in liver and kidney, and eventually slowed down the growth of juvenile Pampus argenteus.

Key words: juvenile Pampus argenteus, breeding density, metabolic enzymes, AST, ALT and LDH gene expression levels