Effects of Dietary Protease Levels on Growth Performance, Feeding Regulation, Glucose and Lipid Metabolism, and Endogenous Protease Secretion in Chinese Perch (Siniperca chuatsi)

300 healthy Chinese perch (<i>Siniperca chuatsi</i>) (34.35 ± 0.47 g) were randomly divided into five groups (P1-P5) fed diets supplemented with 0, 0.2, 0.4, 0.8, and 1.6 g/kg protease for 8 weeks. Compared to P1, protease supplementation significantly up-regulated endogenous pepsinogen genes (<i>pga1</i> and <i>pgc</i>) and down-regulated the muscle deamination gene <i>ampd</i>. In comparison to P1, the expression level of the hepatic gene <i>ast</i> increased in P2, P3, and P5, while <i>gdh</i> elevated in P2 and P3 (<i>p</i> < 0.05). Compared to P1, the expression of feeding-related gene <i>npy</i> decreased while <i>pomc</i> increased in P2; <i>agrp</i> increased in P3; and <i>pomc</i> and <i>cart</i> decreased in P5, resulting in significant increases in feed intake in P2, P3, and P5 (<i>p</i> < 0.05). Glycolytic genes (<i>gk</i> and <i>pk</i>) and lipid metabolism gene <i>pparα</i> were up-regulated in P2, P3 and P5, while <i>hsl</i> increased in P3 but decreased in P5 (<i>p</i> < 0.05). P5 exhibited significantly improved weight gain rate, specific growth rate, protein efficiency ratio, and protein retention rate, alongside reduced feed conversion ratio compared with P1. Therefore, dietary 1.6 g/kg protease significantly enhances growth, improves feed efficiency, stimulates pepsinogen secretion, and modulates deamination, glycolytic, and lipid metabolism genes in <i>Siniperca chuatsi</i>.