Effect of fishmeal replacement with cottonseed protein concentrate on growth, health, and post-nutritional recovery compensatory growth in <italic>Siniperca chuatsi</italic>

Fishmeal replacement is crucial for promoting sustainable aquaculture, and cottonseed protein concentrate (CPC) is considered a promising plant protein source. Currently, the fishmeal constitutes over 50% of commercial diets for Siniperca chuatsi, highlighting the urgency of reducing its proportion to enhance the sustainability of aquaculture industry. This study investigated the tolerance threshold of S. chuatsi to CPC, as well as its effects on growth performance, feed utilization, liver and intestinal health, and compensatory growth during nutritional recovery. Juvenile S. chuatsi [initial weight (34.47±0.07) g] were fed isonitrogenous and isolipidic diets with fishmeal replaced by CPC at levels of 0% (CF0), 17.5% (CF17.5), 35.0% (CF35.0), 52.5% (CF52.5), and 70.0% (CF70.0) for six weeks, followed by a six-week nutritional recovery period with the control diet. Results showed S. chuatsi exhibited lower tolerance to CPC than other carnivorous fish species. Despite essential amino acid supplementation, CPC replacement at 17.5% (151.8 g/kg) or higher significantly reduced weight gain and specific growth rates, while increasing feed conversion ratio and protein efficiency ratio (P P ampk, s6k, gh, igf-1 and lipid metabolism genes (srebp-1, fas, acc1) were significantly upregulated in CF35.0 and CF70.0 (P npy and pomc exhibited brain-specific downregulation but were concurrently upregulated in CF35.0 and CF70.0 in the midgut (P P p53-mediated hepatocyte apoptosis, suggesting the occurrence of severe liver damage. In contrast, the 70% replacement group exhibited increased SOD, CAT, and GPx activities, decreased MDA, ALT, and AST levels (P becn1 upregulation and caspase-3 downregulation. CPC replacement also impaired intestinal health, significantly reducing villus height, width, and muscle layer thickness (P occludin, zo-1) were downregulated (P nos1 was upregulated (P tnf-α, il-1β) were downregulated (P P P mtor, igf-1, srebp-1, and fas (P mtor/s6k during nutritional recovery (P igf-1,srebp-1, and fas returned to control levels (P > 0.05). Meanwhile, pcna and ccnd1 were significantly upregulated (P ampk upregulated ppar-α (P P S. chuatsi. However, during nutritional recovery, S. chuatsi displayed compensatory growth, with weight gain rate, specific growth rate, and protein efficiency increasing with prior CPC replacement levels. Through metabolic remodeling and energy redistribution, growth and tissue repair were effectively restored. These findings provide insights into CPC as an alternative to fishmeal and its significance in developing precision nutrition strategies for sustainable aquaculture.