The potential of processed cassava leaf and root for feeding Nile tilapia

The search for alternative, economical, and sustainable ingredients for aquaculture feed is a constant challenge. Nile tilapia (Oreochromis niloticus) is a fundamental species in global aquaculture production, but the cost of commercial feeds can be a significant barrier, especially for small and medium-sized producers.

A recent scientific study published by scientists from the Norwegian University of Life Sciences and Hawassa University investigates the use of different proportions of processed cassava leaf and root as a substitute for conventional protein and energy sources in diets for Nile tilapia, evaluating their effects on digestibility, growth performance, and production economy. The findings suggest that cassava, a locally available and low-cost resource, could be a key piece in improving the profitability and sustainability of tilapia aquaculture.

Cassava: a nutritious and economical alternative in aquaculture

Cassava (Manihot esculenta) presents itself as a promising ingredient for feeding Nile tilapia due to its nutritional composition and wide availability. Processed cassava leaf can contain a high level of crude protein (between 11.8% and 38.1% of dry matter), while the root is a rich source of metabolizable energy, vitamins, and minerals. Previous studies had already indicated that partial substitution of conventional ingredients with cassava products could improve performance and economy in tilapia production. The omnivorous nature and long digestive tract of Nile tilapia allow it to efficiently utilize these plant products.

The main objective of the research, published in the scientific journal Aquaculture International, was to determine the optimal proportion of processed cassava leaf (as a protein source) and processed cassava root (as a starch source) to maximize digestibility, feed utilization, growth performance, and profitability in the production of Nile tilapia fry.

How was the study conducted?

To carry out the research, investigators collected fresh leaves and roots from cassava plants. These materials were processed by washing, chopping (roots) or pounding (leaves), soaking in water for three days, and subsequent cooking at 80∘C for 10 minutes. Additionally, the processed cassava leaves were subjected to fermentation with fresh rumen fluid. Finally, both products were dried and finely ground.

The scientists formulated five isonitrogenous (similar protein content) and isocaloric (similar energy content) diets:

• A control diet (CL0​CR0​) without cassava meal.
• Four experimental diets with different combinations:
  • CL20​CR50​: 20% of the soybean cake protein replaced by cassava leaf protein and 50% of the wheat flour starch replaced by cassava root starch.
  • CL20​CR75​: 20% protein replacement with cassava leaf and 75% starch replacement with cassava root.
  • CL40​CR50​: 40% protein replacement with cassava leaf and 50% starch replacement with cassava root.
  • CL40​CR75​: 40% protein replacement with cassava leaf and 75% starch replacement with cassava root. Nile tilapia fry, with an average initial body weight of 2.1±0.1 g, were distributed into 250 L tanks (20 fish per tank, with three replicates per treatment) and fed for 14 weeks. Growth parameters, feed utilization, apparent nutrient digestibility were recorded, and an economic analysis of the diets was performed.

Key findings: digestibility, growth, and profitability with cassava diets

Better digestibility with specific cassava proportions

The apparent digestibility coefficients (ADC) of nutrients were significantly influenced by the inclusion levels of fermented cassava leaf and root.

• The CL20​CR50​ and CL20​CR75​ diets showed the highest ADC values for dry matter (DM), crude protein (), ether extract (EE), and gross energy (GE).
• Specifically, fish fed the CL20​CR50​ diet showed higher apparent digestibility in the hindgut for dry matter and ether extract compared to other diets, although similar to the control diet (CL0​CR0​) and the CL20​CR75​ diet.
• The lowest ADC values were consistently observed in diets with higher inclusion of cassava leaf (CL40​CR50​ and CL40​CR75​), probably due to higher fiber content and anti-nutritional factors associated with higher levels of cassava leaf.

Comparable and superior growth performance with cassava

Growth performance also showed promising results for certain cassava formulations.

• Fish fed the CL20​CR50​ diet showed growth performance and protein efficiency ratios comparable to fish fed the control diet (CL0​CR0​) and the CL20​CR75​ diet, being significantly better than the other diets (CL40​CR50​ and CL40​CR75​).
• The final body weight, body weight gain, daily growth rate, and specific growth rate of fish fed the CL20​CR50​ diet were higher than those of other diets, although comparable to the CL0​CR0​ and CL20​CR75​ diets.
• The feed conversion ratio (FCR) was significantly lower (better) for fish fed the CL20​CR50​ diet.

Positive economic impact

From an economic perspective, the use of cassava also proved advantageous.

• The CL20​CR50​ and CL20​CR75​ diets resulted in a higher gross profit margin, a better cost-benefit ratio, and a higher return on investment compared to the other diets, including the control diet.
• This was due to high fish sales combined with relatively low production costs for these diets. For example, the substitution of 20% of soybean cake and 50% of wheat flour (CL20​CR50​), and 20% of soybean cake and 75% of wheat flour (CL20​CR75​) with cassava leaf and root, respectively, reduced production costs by 11.5% and increased profit margins by 18.9% compared to the control diet.

Implications for tilapia fish farming

The results of this study are encouraging for the aquaculture industry, especially for Nile tilapia producers seeking more economical and efficient feed alternatives. The research demonstrates that it is possible to partially replace soybean cake and wheat flour with processed cassava leaf and root without negatively affecting, and even improving in some cases, digestibility, growth, and profitability.

The diets that combined a 20% substitution of soybean cake protein with cassava leaf protein and a 50% or 75% substitution of wheat flour starch with cassava root starch (CL20​CR50​ and CL20​CR75​) stood out for offering the best results in of biological and economic performance. These findings suggest that the inclusion of processed cassava leaf up to a level that replaces 20% of soybean cake protein, and processed cassava root up to a level that replaces 75% of wheat flour starch, is viable and beneficial.

It is important to note that higher levels of cassava leaf inclusion (40% protein substitution) tended to decrease digestibility and performance, likely due to increased fiber content and anti-nutritional factors. This underscores the importance of finding the right proportion and processing methods to reduce these limiting factors.

Conclusion: cassava as a strategic ingredient

In conclusion, the study demonstrates that the CL20​CR50​ and CL20​CR75​ diets, which incorporate processed cassava leaf and root in specific proportions, not only match but in some aspects sur the control diet in of digestibility, feed utilization, growth performance, and, crucially, economic profitability for Nile tilapia production.

These findings position processed cassava as a strategic and promising feed ingredient for formulating more economical and sustainable diets in tilapia aquaculture. The adoption of these dietary proportions of cassava leaf and root is recommended for small and medium-scale Nile tilapia production. Although it is suggested to validate these results under larger-scale production conditions to evaluate long-term effects and ensure full commercial viability, this study opens an important door towards more efficient and profitable aquaculture.

Tigist Ashagre Amare
Department of Animal and Aquacultural Sciences, Faculty of Biosciences, Norwegian University of Life Sciences
Ås, Norway

Department of Aquatic Sciences, Fishery and Aquaculture, Hawassa University
Hawassa, Ethiopia
Email: [email protected]

Reference (open access)
Amare, T.A., Storebakken, T., Mørkøre, T. et al. Different dietary ratios of processed cassava leaf and root for Nile tilapia: Effects on digestibility, growth performance, and production economy. Aquacult Int 33, 331 (2025). https://doi.org/10.1007/s10499-025-02011-x