An 8-week feeding trial was conducted to assess the effects on growth, antioxidant capacity, digestive enzyme activity, and gene expression related to muscle growth and protein synthesis of juvenile greasyback shrimp (
Metapenaeus ensis) using five experimental diets containing 29.37%, 34.30%, 39.11%,
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An 8-week feeding trial was conducted to assess the effects on growth, antioxidant capacity, digestive enzyme activity, and gene expression related to muscle growth and protein synthesis of juvenile greasyback shrimp (
Metapenaeus ensis) using five experimental diets containing 29.37%, 34.30%, 39.11%, 44.05%, and 49.32% of protein. The results demonstrated that juvenile greasyback shrimp consuming 39.11%, 44.05%, and 49.32% dietary protein had a significantly higher final body weight (FBW), weight gain (WG), feed conversion ratio (FCR), and specific growth rate (SGR) than other groups (
p < 0.05). The protein efficiency ratio (PER) showed a significantly quadratic pattern with increasing dietary protein levels
(p < 0.05). The highest trypsin and pepsin activities were observed in the group with a protein level of 44.05% (
p < 0.05). Relatively higher superoxide dismutase (SOD) activity was found in groups with protein levels of 39.11% (
p < 0.05). Alkaline phosphatase (AKP) and catalase (CAT) activity showed a significantly linear increasing pattern with increasing protein intake up to 44.05%, and then decreased gradually (
p < 0.05). Compared to the dietary 29.37% protein level, the expression levels of myogenic regulatory factors (
mef2α,
mlc, and
myf5) and mTOR pathway (
mtor,
s6k,
akt, and
pi3k)-related genes were significantly up-regulated in muscle with 39.11%, 44.05%, and 49.32% dietary protein levels (
p < 0.05). The AAR pathway (
gcn2,
eif2α, and
atf4)-related gene expression levels were significantly lower in muscles with 39.11%, 44.05%, and 49.32% protein levels than in other groups (
p < 0.05). Based on the broken-line regression analysis of SGR, the estimated appropriate dietary protein requirement for juvenile greasyback shrimp is 38.59%.
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