Effects of dietary protein-to-energy ratio on growth performance, body composition, and health status of large-sized grass carp, Ctenopharyngodon idella

Zhangbin Liao^1*Lei Wang^2*Biao Yun²Xiaolin Dong²Fengchi Niu²Jian Wang²Xueqiao Qian²Xueming Hua³

• ¹Guangdong Haid Group Co., Ltd, Guangzhou, China
• ²Guangdong Haid Group Co Ltd, Guangzhou, China
• ³Shanghai Ocean University, Shanghai, China

A 56 days feeding trial was performed to investigate the effects of dietary protein-to-energy (P/E) ratio on the growth performance, body composition, and health status of large-sized grass carp, Ctenopharyngodon idella. Fish (initial body weight 2200.4 ± 79.3 g) were randomly fed one of the six isolipidic and isoenergetic diets (gross energy 10 kJ/g), which were formulated with various P/E ratios (21.7, 23.7, 24.9, 27.1, 29.2, and 31.5 mg/kJ) and named as P/E 21.7, P/E 23.7, P/E 24.9, P/E 27.1, P/E 29.2 and P/E 31.5, respectively. After the feeding trial, the best growth performance was observed in the group P/E 29.2, which had the highest weight gain. In addition, fish fed the optimal P/E diet exhibited a superior health status in terms of tissue histology, and biochemical analyses of serum and liver. The liver transcriptome assay revealed that a suitable P/E ratio potentially enhances growth performance and immune function by modulating the AMPK signaling pathway, Ras signaling pathway, and arachidonic acid metabolism, as well as affecting rRNA synthesis via regulating the ribosome biogenesis genes expression in eukaryotes. Based on the second-order polynomial regression analysis of the growth performance and health status against P/E, the optimal P/E range was 27.36 - 28.93.