ABSTRACT Aquaculture is rapidly expanding, with Nile tilapia (Oreochromis niloticus) being a key freshwater species. Rising fishmeal (FM) costs and environmental concerns have increased interest in sustainable alternative protein sources. This study evaluated the effects of diets containing soybean (SB) or Kappaphycus sp. on the growth, feed efficiency and nutrient digestibility of Nile tilapia (O. niloticus). Four dietary treatments were tested over a 62‐day feeding trial: FM diet, a diet containing SB, Kappaphycus sp. (seaweed SW) and a natural meal (NM) serving as a negative control. Diets were formulated to be isoproteic (360 g/kg) and isocaloric (3600 kcal/kg). Growth performance, feed utilization, apparent nutrient digestibility and economic efficiency were assessed. Fish fed SB and SW diets exhibited final body weight, weight gain, specific growth rate and condition factor comparable to those of fish fed the FM diet and significantly superior to those of the NM group (p < 0.05). Feed intake and feed conversion rate did not differ significantly among FM, SB and SW diets, although the SW diet resulted in the highest protein efficiency ratio and lowest protein intake. Apparent digestibility coefficients varied among diets: Protein digestibility was highest in the SW diet, whereas FM showed superior digestibility for dry matter, fat and energy. Economic analysis revealed lower incidence costs and higher profitability indices for SB and SW diets compared with FM. These findings demonstrate that, under the conditions of this study, SB meal and Kappaphycus sp. can effectively replace FM in Nile tilapia feeds without compromising growth or feed efficiency while improving economic viability and supporting the development of sustainable aquafeeds.
Viagem et al. (Sun,) studied this question.