Fermentation of rice milling by-products can completely replace soybean meal in the diet of Oreochromis niloticus fingerlings

The expansion and intensification of aquaculture have been widely adopted to support large-scale production, creating a reliance on high-protein feed ingredients such as soybean meal (SBM) and fish meal (FM). These ingredients, however, are costly and unsustainable, emphasizing the need for alternative plant-based protein sources for aquafeeds. This study assessed the nutritional and feed value of fermented rice bran meal (FRBM) as a substitute for SBM in the diet of tilapia ( Oreochromis niloticus ) fingerlings. Five diets were formulated with FRBM replacing SBM at 0%, 25%, 50%, 75%, and 100%, and were fed to fingerlings over a 60-day period. Results showed that FRBM could fully replace SBM, with growth-promoting effects particularly observed at 25% replacement. Survival, percentage weight gain, feed conversion ratio (FCR), and specific growth rate (SGR) did not differ significantly among the treatments with varying FRBM levels. No significant differences in carcass composition (protein, lipid, and ash) were observed among tilapia fed with diets containing FRBM replacement. The apparent protein and dry matter digestibility coefficients of FRBM are 91.52% and 66.67%, respectively. Histological examination also revealed no intestinal abnormalities, even at the highest level of FRBM inclusion. Overall, the findings suggest that solid-state fermented rice bran can fully replace soybean meal in the diet of O. niloticus . In addition, its use presents a practical option to help meet the growing protein requirements in aquafeeds and to promote the sustainable expansion of tilapia aquaculture.