Influence of dietary soybean meal replacement with yellow mealworm (Tenebrio molitor) on growth performance, antioxidant capacity, skin color, and flesh quality of mirror carp (Cyprinus carpio var. specularis)

Abstract

Yellow mealworms (TM) are currently receiving increasing attention as dietary protein source in aquaculture. A 60-day feeding trial was conducted to study the effects of dietary soybean meal (SM) replacement by TM on growth performance, antioxidant capacity, and flesh quality of mirror carp. A total of 630 mirror carp were fed seven diets containing graded concentrations of TM: YM0 (control), YM15, YM30, YM45, YM60, YM75, and YM100, corresponding to 0%, 15%, 30%, 45%, 60%, 75%, and 100% dietary soybean meal replacement. The results indicated dietary TM significantly improved the final body weight (FBW), specific growth rate (SGR), and protein efficiency (PE) (P < 0.05), except for YM100 (P > 0.05). The antioxidant capacity was promoted by increasing muscle total antioxidant capacity (T-AOC) in YM30 and superoxide dismutase (SOD) activity in TM supplemented groups (P < 0.05). The nutritional value was significantly boosted by increasing the muscle protein of YM45 and YM60 groups, the whole-body protein and muscle glycine and proline of YM60 group, and the muscle arginine of YM100 group (P < 0.05). The economic value of mirror carp also increased with the improvement of skin color by increasing yellowness (b*) (P < 0.05). Furthermore, all muscle textural parameters, fiber density, sarcomere length, and the mRNA expression of genes involved in muscle cell growth had similar change trends, increasing initially and then declining with the increase of dietary TM level. The muscle chewiness, cohesiveness, and mfr4 expression in YM15, and the adhesiveness, fiber density, sarcomere length, and mRNA expression of fgf in YM45 were higher than in the control and YM100 (P < 0.05), while no difference was found between control and YM100 (P > 0.05). The mRNA expression levels of myhc and TOR in the muscle of YM60 were significantly higher than those of the control group (P < 0.05), while there was no significant difference in YM100 (P > 0.05). According to the results of principal components analysis (PCA), the muscle textural properties in YM45 were optimal among all groups. As a consequence, TM would be able to completely replace dietary soybean meal without negative influences on growth performance, antioxidant capacity, or flesh quality of mirror carp. Finally, based on FBW, muscle crude protein, muscle fiber diameter, and protein retention efficiency (PRE), the optimal levels of dietary soybean meal replaced by TM were 50.14%, 52.43%, 53.60%, and 55.35%, respectively.