Abstract:
This study was conducted to investigate the effects of low soybean meal amino acid balanced diets on growth performance, health status, and muscle quality of
Ctenopharyngodon idella. Four isonitrogenous and isoenergetic diets were formulated with soybean meal contents of 20% (control group, D20), 19% (D19), 18% (D18), and 17% (D17). Lysine, methionine, threonine, valine, and tryptophan were supplemented to ensure identical essential amino acid levels across all dietary groups. Over a 56d feeding trial, survival rate (SR), hepatosomatic index (HSI), condition factor (CF), and viscerosomatic index (VSI) did not differ significantly among groups, whereas weight gain rate (WGR), specific growth rate (SGR), protein deposition rate (PDR), and feed conversion ratio (FCR) showed significant differences. In particular, WGR, SGR, and PDR in the D17 group increased by 30.09%, 14.79%, and 38.76%, respectively (
P<0.05), while FCR decreased by 17.78% (
P<0.05). Serum glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) activities were significantly higher in the D20 group than that in the other groups (
P<0.05), while the high-density lipoprotein cholesterol (HDL-C) level was significantly lower (
P<0.05). The total antioxidant capacity (T-AOC) in the liver of the D20 group was significantly lower than that of the other groups (
P<0.05), malondialdehyde (MDA) level was significantly higher (
P<0.05), and catalase (CAT) activity was significantly lower than in the D18 and D17 groups (
P<0.05) but comparable to that in the D19 group. Reduction of soybean meal content coupled with amino acid balancing in the feed improved hepatic cell integrity and increased intestinal villus height. Regarding muscle quality, the density of muscle fibers tended to decrease and fiber diameter to increase as soybean meal content decreased. Moreover, the hardness of muscle in the D20 group was significantly higher (
P<0.05), and the chewiness was significantly lower (
P<0.05) than that in the other groups. Amino acid balancing also promoted the gene expression of
pi3k,
akt,
mtorc1,
4ebp1, and
s6k1 (
P<0.05), thereby enhancing protein synthesis. In conclusion, amino acids balancing to replace 15% of soybean meal (from 20% to 17%) in the diet of
Ctenopharyngodon idella not only significantly improved growth performance and antioxidant capacity of
Ctenopharyngodon idella, but also enhanced muscle texture characteristics. These results provide data support for reducing the use of soybean meal in aquafeeds.