2.2.2. Sample Handling

After all the samples were collected, the blood samples were centrifuged at 3500 rpm for 10 min at 4 ◦C using a cryogenic freezing centrifuge, and the upper serum layer was packed into lyophilized tubes and stored in a −80 ◦C refrigerator. The intestinal tissues were stored in a −80 ◦C refrigerator.

After thawing, the intestinal tissues were accurately weighed and added to 9 times the volume of saline at a ratio of mass (g): volume (mL) = 1:9, which was then homogenized at 4 ◦C using a freezing homogenizer (MYD-48) to produce a 10-fold dilution of homogenate. The supernatant was then centrifuged at 2500 r/min for 10 min at 4 ◦C, after which it was used to determine the activity of intestinal digestive enzymes.

#### *2.3. Index Measurement*

2.3.1. Growth Performance Parameters' Measurements

Feed coefficient (FC), weight gain rate (WGR, %), specific growth rate (SGR, %), condition factor (CF, %), hepatosomatic index (HSI, %), and viscerosomatic index (VSI, %) were calculated as follows:

$$F \subset W\_f / (\mathcal{W}\_t - \mathcal{W}\_0)\_\prime \tag{1}$$

$$WGR = \left(W\_t - W\_0\right) / W\_0 \times 100\% \tag{2}$$

$$SGR = (\ln \mathcal{W}\_t - \ln \mathcal{W}\_0) / t \times 100\%,\tag{3}$$

$$
\mathbb{C}F = \mathcal{W}\_t / L^3 \times 100\%,\tag{4}
$$

$$HSI = \mathcal{W}\_l / \mathcal{W}\_t \times 100\%\_t \tag{5}$$

$$VSI = W\_{\overline{v}} / W\_{\overline{t}} \times 100\%.\tag{6}$$

*Wf* is the total feeding of the fish on day t at the time of measurement, *Wt* is the mass of the fish measured at the time of the final sampling (g), *W*<sup>0</sup> is the mass of the fish measured at the time of the initial sampling (g), *t* is the number of days of breeding (d), *L* is the body length of the fish at the time of measurement (cm), *Wl* is the mass of the fish's liver at the time of sampling (g), and *Wv* is the mass of the fish's visceral mass at the time of sampling (g).
