Utilization of Byproducts in the Diet of Oreochromis niloticus: Impact of Probiotic Supplementation on Zootechnical Performance and the Biochemical Composition of the Flesh

Abstract

The high cost of conventional aquaculture feed and the need for sustainable feeding strategies have encouraged the use of locally available agricultural by-products in fish diets. Fermentation and probiotic supplementation may improve the nutritional utilisation of these alternative feed resources while supporting fish growth, physiological condition, and flesh quality. However, information on the combined use of fermented agricultural by-products and probiotics in diets for Oreochromis niloticus remains limited, particularly under Côte d’Ivoire aquaculture conditions. This study evaluated the zootechnical performance and biochemical composition of Oreochromis niloticus fed diets formulated from fermented agricultural by-products, with and without probiotic supplementation. Three dietary treatments were evaluated over a seven-week feeding period: a commercial diet used as the control; a diet formulated from fermented agricultural by-products and supplemented with probiotics (Saccharomyces cerevisiae and Bacillus amyloliquefaciens) (DWP); and a similar formulated diet without probiotic supplementation (DFP). Growth performance, selected welfare indicators, and biochemical parameters of fish flesh were assessed. No significant differences were observed among treatments for growth-related parameters. Specific growth rates were 0.53 ± 0.03, 0.62 ± 0.06, and 0.48 ± 0.08 % day-1 for the control, DWP, and DFP treatments, respectively. In contrast, significant differences were observed for welfare-related indicators, particularly the gonadosomatic index, which reached 1.12 ± 0.19 % for fish receiving the probiotic-supplemented diet, compared with 0.78 ± 0.05 % in the control and 0.55 ± 0.12 % in the non-supplemented diet. Biochemical characterisation of fish flesh also revealed significant differences among treatments. Reducing sugar contents were 2.68 ± 0.17, 3.25 ± 0.17, and 5.05 ± 0.12 mg g⁻¹ in the control, DWP, and DFP groups, respectively. Total polyphenol contents were likewise significantly different, reaching 8.55 ± 0.10 mg EG g⁻¹ in the control, 14.73 ± 0.85 mg EG g⁻¹ in DWP, and 17.32 ± 0.29 mg EG g⁻¹ in DFP. These results highlight the potential of fermented agricultural by-products supplemented with probiotics as alternative feed ingredients for O. niloticus production and provide a foundation for further research into their nutritional, functional, and sustainability properties in aquaculture.