Abstract:
To evaluate the effects of flow-velocity acclimation on growth, skeletal muscle development, antioxidant function, and carbohydrate–lipid metabolism in juvenile
Gymnocypris przewalskii, and to identify an appropriate rearing flow velocity. Four flow-velocity treatments were established: 0 bl/s (still water group, C), 1.2 bl/s (low-flow group, L1), 2.4 bl/s (medium-flow group, L2), and 3.6 bl/s (high-flow group, L3), followed by a
60 d rearing trial. Growth and feed intake were recorded. Histological observations were performed on dorsal skeletal muscle and liver. Enzyme activities and gene expression related to muscle growth and hepatic antioxidant capacity were determined, and biochemical indices associated with carbohydrate–lipid metabolism were measured. Differences among groups were analyzed using ANOVA followed by multiple comparisons. Final body weight in L2 (6.46 ± 0.34) g was significantly higher than that in L3 5.63 ± 0.22) g (
P < 0.05), and weight gain rate (111% ± 18%) was significantly higher than in the other groups (
P < 0.05). Feed intake rate and specific growth rate were reduced in L3 (
P < 0.05). Histological analysis showed that muscle fiber cross-sectional area was significantly increased in L1 (
P < 0.05), whereas it was significantly decreased in L3 (
P < 0.05). At the molecular level, flow-velocity treatments promoted muscular
igf gene expression, with the highest relative expression observed in L2 (
P < 0.05); in L3,
mtor and
akt expression levels were significantly reduced and accompanied by an upregulation of
foxo3 (
P < 0.05). Regarding antioxidant responses, hepatic T-SOD and CAT activities were enhanced in L1 (
P < 0.05), and muscular T-SOD activity in L1 and L2 was higher than that in L3 (
P < 0.05). Metabolic indices further suggested differential substrate utilization under medium and high flow velocities. Under the present experimental conditions, 2.4 bl/s was more favorable for maintaining growth performance, 1.2 bl/s was more beneficial for improving muscle structure and enhancing antioxidant capacity, whereas 3.6 bl/s may increase metabolic load and suppress growth-related anabolic signaling.