DIETARY FISHMEAL REPLACEMENT WITH ABALONE VISCERA HYDROLYZED PROTEIN ON GROWTH PERFORMANCE, HEPATIC ANTIOXIDANT CAPACITY, AND INTESTINAL HEALTH IN SPOTTED SEA BASS (LATEOLABRAX MACULATUS)

To investigate the optimal replacement level of fishmeal with abalone viscera hydrolysate (AVH) in the diet of spotted sea bass (Lateolabrax maculatus) and its effect on fish health, a feeding trial was conducted for 8 weeks. Juvenile spotted sea bass [initial body weight: (141.22±0.38) g] were fed five isonitrogenous and isolipidic diets with AVH replacing 0, 10%, 20%, 30%, and 40% of fishmeal, respectively. Growth performance, serum biochemistry, hepatic antioxidant parameters, intestinal digestion, and gut microbiota (via 16S rRNA sequencing) were analyzed. Results showed that the specific growth rate was the highest in 30% replacement group, with no significant difference compared to the control. In the 40% replacement group, the activities of alanine aminotransferase and aspartate aminotransferase were significantly increased, and hepatic malondialdehyde content was significantly elevated, indicating liver oxidative damage. Serum immune parameters showed that complement C4 content was increased while immunoglobulin M (IgM) level was significantly decreased in the 40% group, suggesting immune dysfunction. Intestinal morphology analysis revealed significantly reduced villus height with loose structure, along with significant increases in D-lactate and diamine oxidase levels in the 40% group. Trypsin activity decreased with increasing replacement level, whereas lipase and amylase activities showed no significant changes. Gut microbiota analysis indicated that the relative abundance of the genus Cetobacterium first increased and then decreased with increasing AVH inclusion, peaking in the 20% replacement group. This study demonstrates that replacing 30% of fishmeal with AVH does not adversely affect the growth, liver function, or intestinal health in spotted sea bass. However, replacement at 40% leads to liver metabolic disorders, oxidative stress, intestinal structural damage, and impaired digestive function.