and centrifuging at 4000 rpm for 10 min at 4 °C, serum samples were
collected and stored at −20 °C for immune analyses. Three fish per
tank were randomly collected for sampling digestive tissues. The liver
and intestine of each fish were excised and the adipose tissue carefully
cleaned. Then samples were rinsed and homogenized with chilled
normal saline solution (1:3 w/v) using an electric blender operating at
8000 rpm for 30 s each time. The homogenate was centrifuged at
10,000 ×g, 4 °C for 30 min to eliminate tissue debris and lipids. The
supernatant of the enzyme extract was gently pipetted into 1.5-mL
Eppendorf tubes and frozen at −20 °C until enzymatic assay. Each
sample preparation step was conducted on ice to maintain a low
temperature. Three additional fish were randomly sampled from each
tank, and each fish was minced, pooled, and frozen at −20 °C for
whole-body proximate composition analysis.