There were three strains of gibel carp in the present study, and they were all from the hatchery of the Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan, Hubei, China. Before the formal trial, a prefeeding period was conducted for 4 weeks to acclimate to the feed and rearing conditions. Then, three strains of the experimental fish were pooled after 24 h starvation. Fish of each strain with the similar weight (3.02 ± 0.82 g) were selected, weighted, and distributed into round fiberglass tanks at the density as 30 fish per tank. Each strain had 9 tanks, respectively, fed by cornstarch (CS) diet, wheat starch (WS) diet, and wheat flour (WF) diet in triplicate, and there were 27 tanks in total (3 strains∗ 3 diets∗ 3 duplication). The fish were fed to apparent satiation twice a day at 08 : 30 am and 14 : 30 pm and reared in the circulating water system: water volume of each tank was 300 L; diameter of tank was 100 cm; water flow rate was 1.8 L min−1; water temperature was 25.5 ± 1.5°C; light intensity was approximately 3 μmol m−2 s−1 at the water surface; light period was from 08 : 00 am to 20 : 00 pm; water dissolved oxygen was more than 5 mg L−1; water ammonia nitrogen was less than 0.5 mg L−1; and water residual chloride was less than 0.01 mg L−1 (weekly monitored).
The feeding trial lasted for 8 weeks. Then, all fish in each tank were weighed after 24 h of food deprivation, and 4 fish per tank were randomly sampled and frozen at -20°C for whole-body composition analysis. The rest of the fish continued refeeding for one more week; 3 fish/tank were randomly sampled at 6 h after the last meal. They were anesthetized by MS-222 (100 mg L−1 tricaine methane sulfonate, Argent Chemical Laboratories Inc., Redmond, WA, USA). After that, blood was collected and then centrifuged at 3000 g, 4°C, 15 min, to obtain the plasma; fresh liver, middle intestine, and muscle (biopsies) of the fish were separated on the ice, immediately frozen in liquid nitrogen, and then kept at -80°C for further analysis.
The feeding trial lasted for 8 weeks. Then, all fish in each tank were weighed after 24 h of food deprivation, and 4 fish per tank were randomly sampled and frozen at -20°C for whole-body composition analysis. The rest of the fish continued refeeding for one more week; 3 fish/tank were randomly sampled at 6 h after the last meal. They were anesthetized by MS-222 (100 mg L−1 tricaine methane sulfonate, Argent Chemical Laboratories Inc., Redmond, WA, USA). After that, blood was collected and then centrifuged at 3000 g, 4°C, 15 min, to obtain the plasma; fresh liver, middle intestine, and muscle (biopsies) of the fish were separated on the ice, immediately frozen in liquid nitrogen, and then kept at -80°C for further analysis.
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