Physiological, Nutritional and Transcriptomic Responses of Sturgeon (Acipenser schrenckii) to Complete Substitution of Fishmeal with Cottonseed Protein Concentrate in Aquafeed

SIMPLE SUMMARY: Cottonseed protein concentrate (CPC) is a high-protein product derived from widely available cottonseed flakes, but its use is limited by the presence of anti-nutritional components (gossypol, etc.). This study investigated the potential of using CPC as a substitute for fishmeal in the diet of sturgeon (Acipenser schrenckii). The study found that completely replacing fishmeal with CPC had negative effects on the growth and physiology of the sturgeon, as shown by reduced weight gain, feed efficiency, and essential amino acids. Additionally, there was a decrease in digestive enzyme activity and an upregulation of genes linked to metabolism in the liver. The research concluded that CPC should not completely replace fishmeal in the diet of the sturgeon. This study provides important data for the development of better aquafeeds and the evaluation of diet performance in sturgeon using molecular methods. Although plant proteins such as CPC can reduce production costs in aquaculture, their excessive consumption can lead to the loss of growth performance and digestion due to anti-nutritional components. ABSTRACT: This study estimated the effect of substituting fishmeal completely with cottonseed protein concentrate (CPC) in the diet of sturgeon (Acipenser schrenckii) on growth, digestive physiology, and hepatic gene expression. A control diet containing fishmeal and an experimental diet based on CPC was designed. The study was conducted for 56 days in indoor recirculating aquaculture systems. The results showed that weight gain, feed efficiency, and whole-body essential amino acids (EAAs) all decreased significantly in the experimental group, while whole-body non-essential amino acids (NEAAs) and serum transaminase activity increased (p < 0.05). The activity of digestive enzymes in the mid-intestine was significantly reduced (p < 0.05), and liver histology revealed fatty infiltration of hepatocytes. The hepatic transcriptome revealed an upregulation of genes linked to metabolism, including steroid biosynthesis, pyruvate metabolism, fatty acid metabolism, and amino acid biosynthesis. These findings indicate that fully replacing fishmeal with CPC harms A. schrenckii growth and physiology. This study provides valuable data for the development of improved aquafeeds and the use of molecular methods to evaluate the diet performance of sturgeon.