Apparent Protein Digestibility and Growth Performance of Nile Tilapia (Oreochromis niloticus L.) Fed on Sunflower and Cotton Seed Meal as Substitutes for Freshwater Shrimp Meal (Caridina nilotica)

Abstract

Fish feed is critical in aquaculture production, accounting for over 60% of operational costs, with protein being the most expensive component. Traditionally, fish meal (FM) has been the primary protein source. However, due to declining capture fisheries and high demand, FM has become scarce and costly, necessitating the search for alternative, low-cost, and nutritionally balanced protein sources. A 180-day feeding experiment was conducted to evaluate the effects of replacing FM with a combination of cottonseed and sunflower meal (SFM) in Nile tilapia diets on growth performance, protein digestibility, and economic returns. Freshwater shrimp meal was replaced at 25%, 50%, 75%, and 100% (diets D1, D2, D3, and D4) and compared to the control diet (D0) containing only FM. Monosex Nile tilapia fingerlings (25 ± 0.01 g) were allocated to 15 cages within an 800 m² earthen pond. Fish on diets D0 and D1 showed superior growth performance metrics, including final mean body weight, weight gain, daily weight gain, specific growth rate, feed conversion ratio, and survival rate (p > 0.05), compared to diets D2, D3, and D4. Growth performance declined significantly with increasing levels of the plant protein mixture (p < 0.05). Diet D0 had the highest apparent protein digestibility, while D4 had the lowest. Cost-benefit analysis revealed that diet D0 had the highest production cost, followed by diets D1, D2, D3, and D4, with no significant cost difference between D0 and D1 (p > 0.05). Thus, the plant protein mixture can effectively replace FM at a 25% inclusion level in Nile tilapia diets.