Valorization of areca byproducts: Enhancing growth, health, and muscle quality of grass carp through a functional feed additive

This study evaluated the dose-dependent effects of immature areca seed (IAS) powder, a major byproduct of areca nut processing, as a functional feed additive for grass carp ( Ctenopharyngodon idella ). In a 56-day feeding trial, dietary supplementation with low-dose IAS (0.5 g/kg) significantly improved growth performance, increasing the weight gain rate by 40.1% and reducing the feed conversion ratio by 19.2% compared to the control. Medium-dose IAS (1.0 g/kg) uniquely enriched the probiotic Cetobacterium in the hindgut, which was associated with improved gut health. In contrast, high-dose IAS (2.0 g/kg) induced a distinct shift in the gut microbiota, marked by the enrichment of Methylocystis and other taxa. Furthermore, IAS supplementation enhanced muscle quality by increasing essential amino acids, beneficial polyunsaturated fatty acids (EPA and DHA), and improving texture profiles (hardness and chewiness). The results demonstrate that IAS can be effectively valorized as a multifunctional feed ingredient, with its effects being highly dose-specific. This work provides a scientific basis for the potential integration of this agricultural byproduct into aquatic feed formulations.