The Effect of Dietary Incorporation of Olive Oil Extraction By-Products on Production Performance and Carcass Traits in Nile Tilapia (Oreochromis niloticus): A Comprehensive Review

Abstract

The imperative for sustainable aquaculture necessitates the identification of alternative feed resources to circumvent the economic and environmental constraints associated with conventional ingredients such as fishmeal and soybean meal. Simultaneously, the olive oil industry generates substantial quantities of by-products—olive pomace (OP), olive mill wastewater (OMW), and olive leaves (OL)—whose disposal poses significant ecological challenges due to their high polyphenolic content and organic load. This manuscript provides a critical synthesis of contemporary research on the valorization of these olive by-products (OBPs) as functional dietary components in feeds for Nile tilapia (Oreochromis niloticus). OBPs are characterized by a complex matrix of fiber, residual protein, and, most notably, a diverse profile of bioactive compounds including phenolics (e.g., hydroxytyrosol, oleuropein) and unsaturated lipids. A meta-analysis of empirical studies indicates that moderate dietary inclusion (5-15%) of appropriately processed OBPs can enhance zootechnical parameters such as weight gain (WG) and feed conversion ratio (FCR), primarily through the amelioration of gut health, nutrient digestibility, and metabolic efficiency. Furthermore, OBPs exert profound positive effects on carcass quality, modulating the fillet's fatty acid profile towards a healthier composition rich in monounsaturated fatty acids (MUFAs) and enhancing oxidative stability post-harvest due to their potent antioxidant properties. This review concludes that the strategic integration of processed OBPs into tilapia aquafeeds constitutes a paradigm of circular bioeconomy, simultaneously mitigating the environmental impact of agro-industrial waste and enhancing the sustainability and economic viability of aquaculture production.