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Four experimental trials were conducted to explore the optimal dietary protein requirement level for the genetically improved farmed tilapia (GIFT) at different seasonal growth stages. Six practical diets were prepared with graded protein levels (26.45%, 29.28%, 31.69%, 33.68%, 36.18% and 38.75%, dry basis). In Stage 1 (initial weight 3.00 g), the results showed that the optimal growth performance was observed in the 33.68% dietary protein group. Correspondingly, compared with the lowest (26.45%) or highest (38.75%) dietary protein groups, 33.68% dietary protein significantly upregulated the GH‐IGF axis‐related genes (GH, GHR1, GHR2 and IGF‐1) and TOR signalling pathway‐related genes (TOR, S6K1 and 4EBP1). In Stage 2 (initial weight 43.78 g), 26.45% dietary protein contributed to the optimum growth performance. Besides, the expression levels of GH, GHR2 and IGF‐1 and TOR signalling pathway (S6K1 and 4EBP1) decreased with the increasing dietary protein levels, and the maximum values were observed in the 26.45% dietary protein group. In Stage 3 (initial weight 99.97 g), the best growth performance was found in the 31.69% dietary protein group. In addition, the mRNA expression levels of GH, IGF1, S6K1 and 4EBP1 increased with the increase in dietary protein levels up to 31.69%, then gradually declined. In Stage 4 (initial weight 302.82 g), dietary protein levels did not affect the growth performance. Based on the quadratic regression analysis of the SGR, the optimal dietary protein level of each stage was estimated to be 33.08% (Spring, Stage 1), 26.45% (Summer, Stage 2), 33.06% (Autumn, Stage 3) and 26.45% (Winter, Stage 4) of dry diet. [ABSTRACT FROM AUTHOR]