Embracing Holistic Formulation Strategies to Maximise Positive Outcomes in Aquaculture Nutrition

Aquaculture nutrition has significantly advanced over the last few decades, mostly in two key research areas: (1) defining the nutrient requirements of diverse species and (2) enhancing ingredient development to empower effective feed formulation. Despite this progress, challenges continue to arise from an expanding diversity of aquaculture species and farming conditions, along with the increasing pressure to meet environmental, social and governance (ESG) expectations which apply constraints on nutrient source and supply in aquafeeds. Research strategies need to evolve to account for more factors influencing real-world aquaculture production, and to that point, there is a need to reevaluate the formulation approaches adopted by aquaculture nutrition research (Table 1). Focus on pushing boundaries, cutting-edge innovation. Strong integrity, ownership and curiosity in research. Willingness to take risks and explore low-performing treatments. Clear commercial interest ensures practical applications. Strong focus on validation and adding value to ingredients. Pushes ingredient inclusion rates to maximise performance. Strong commercial focus ensures economic feasibility. Uses a co-ingredient replacement approach, considering overall feed value. Extensive engagement with digestibility studies. Flexible approach, blending methodologies from academics, ingredient companies and feed mills. Strong commercial focus ensures industry relevance. Lack of commercial interest, limiting direct industry application. Formulation approach primarily focused on single-ingredient assessment, which may not translate well to commercial feed formulations. Conservative approach limits risk-taking and potential breakthroughs. May overemphasise product validation rather than broader nutritional strategies. Conservative approach hinders rapid adoption of novel ingredients. Limited interest in fundamental research beyond commercial value. Conservative approach may limit risk-taking and innovation. Potential for bias based on client needs rather than scientific objectivity. Can lead fundamental discoveries that influence long-term industry advancements. Potential for collaboration with ingredient companies to validate innovations. Can work with academics to validate novel ingredients. Potential to influence feed mills by demonstrating ingredient benefits. Can use ingredient studies from academic and ingredient company research to screen potential winners and losers before second stage assessment internally. Opportunity to drive ingredient demand through practical applications. Can bridge gaps between research and commercial application. Opportunity to guide formulation strategies based on multiple perspectives. Misalignment with industry needs may reduce the impact of research. Lack of immediate commercial viability can limit funding and adoption. High inclusion rates may not always align with feed formulation realities. Dependence on benchmarking against existing industry standards may limit innovation. Dependence on established formulations may reduce adaptability to emerging innovations. Pressure for cost-effectiveness may limit investment in novel feed components. Reliant on client demands, which may restrict independent innovation. Risk of favouring short-term commercial gains over long-term advancements. Traditionally, emphasis was placed on ingredients instead of nutrients, with the exception of researching nutrient requirements. Traditional methods have concentrated on evaluating individual ingredients by characterisation, palatability, digestibility, utilisation and functionality [1]. In recent years, additional steps such as processing effects, immunological responses and sustainability assessments have been introduced [2]. This approach is well suited for single-ingredient assessments to allow for the judicious application of any single ingredient in a formulation, providing a clear causational effect and ease of experimentation. Adoption of the single ingredient assessment approach has been reinforced during the fishmeal and fish oil reduction focus era (early 2000s to 2019) through value-adding strategies seeking to replace them with alternative ingredients, often by claiming similar or slightly improved performance with replacement in the hope of securing a premium price against other alternatives. While most ingredient alternatives have benchmarked themselves against fishmeal or fish oil, the use of these resources remains higher than ever before. In 2020, an estimated 4.1 million tonnes of fishmeal were used in aquaculture feeds, up from 3.2 million tonnes in 2000 [3] (Figure 1). The strategy of fishmeal replacement with a single novel ingredient has failed, whereas the strategy of co-inclusion of ingredients where multiple ingredients are replaced simultaneously has proven more effective. By 2020, fishmeal accounted for less than 10% of global feed ingredient use, compared to 19% in 2000. Increasing sustainability pressures, the need for economic efficiency and efforts to mitigate environmental impacts—combined with the overwhelming availability of feedstuffs, such as additives and novel ingredients—demand a shift in research focus. To ensure successful and effective translation of research outputs into industry practices, a balanced transition towards a co-ingredient or co-inclusion formulation approach should be considered by stakeholders in aquaculture nutrition research, rather than seeking the perfect ingredient, given it is widely used by industry (Table 1). To drive meaningful change and encourage industry adoption of research findings, it is important to shift towards a comprehensive and well-planned inclusion strategy in feed formulation [2]. This requires a deeper knowledge of each ingredient's composition and its variabilities in nutrient supply. Modern diets, based on precision nutrition, necessitate an understanding of digestible nutrients and energy profiles, palatability and potential antinutrient or indigestible content within each ingredient, as well as their overall inclusion tolerance [4-6]. While a feed can basically be produced from any macronutrient sources, factors like antinutrients, indigestible components and palatability remain central to effective feed formulation [3]. Why change? Traditional focus on single-ingredient assessment, where a targeted ingredient is replaced with an alternative, and only minor adjustments (up to 2%–3% inclusion rates) are made to balance the formulation (e.g., replacing fishmeal with a novel protein source, with slight adjustments to protein-rich ingredients and flours; Table 2), limits understanding of complex feed interactions. Understanding the potential for inclusion broadens research relevance and impact by enhancing industry adoption. In a linear-least-cost feed formulation programme, the process is managed by defining nutritional targets, or nutrient levels, for the diet being produced. Constraints are then imposed on each ingredient available, setting upper and lower boundaries for their inclusion. Beyond physical and chemical properties, formulation constraints also encompass economic, social, legal and sustainability factors influencing the information required upfront during the technical data sheet stage [2]. For example, an ingredient's carbon footprint can significantly impact its future viability [7]. When introducing a new ingredient, its inclusion is primarily guided by its composition and value, outside the established boundary-setting processes. Most factors on aspects like palatability and so on become arbitrary assignments based on the formulator's experience and become where those boundaries are influenced. But when we do include a new ingredient, what inevitably happens is not a process of full or partial replacement, but rather one of complementary introduction [8]. Where a new ingredient gets included all the other ingredients tend to reduce by a marginal amount [9, 10], or conversely when we seek to exclude a single ingredient, we increment up each of the others, as one-on-one replacement is challenging due to nutrient composition differences between the two ingredients [10]. Such an approach exacerbates the risk in formulation, whereas incremental complementarity (co-ingredient replacement; Table 2) allows for a risk reduction approach [1]. This opinion piece aims to (1) discuss and contextualise the merits, limitations and impacts of various formulation approaches; (2) challenge current academic practices and provide insights that can enhance the translation of research outputs into practical outcomes in the post fishmeal and fish oil reduction focus era and (3) encourage further engagement amongst research organisations and industry. The single-ingredient assessment approach while straightforward and potentially providing some understanding of how individual ingredients influence animal nutrition and feed characteristics, only works if the ingredient being included is very close in nutritional characteristics to the one being replaced, which is nearly impossible and typically results in nutrient imbalances in the formulation [11]. For the most part it is an impractical and overly ingredient-focused approach. In contrast, the co-ingredient replacement approach offers a broader impact in the context of industry adoption and greater flexibility by considering the combined effects of multiple ingredients in the feed matrix and allowing the diet to be balanced so the effects of ingredients can be isolated from the effects of nutrients [8]. Although less targeted, it provides a more comprehensive consideration of the factors influencing the feed. This method requires careful characterisation of the ingredients being replaced, and those added and an understanding of the interaction between their nutritive factors, whether antagonistic or synergistic. The practice of substituting single ingredients tends to focus on the effects of isolated components, which is beneficial for examining specific aspects like an ingredient's palatability, neglecting the complex interactions within the feed matrix. In contrast, the co-ingredient replacement strategy introduces a more holistic perspective by prioritising key factors—understanding the potential use of each ingredient, ensuring the supply of digestible nutrients and determining the availability of metabolic energy are all essential. These considerations are foundational because growth studies that do not account for well-balanced formulations in terms of digestible nutrients and energy are likely to produce misleading results [11]. Due to its complexity and more subtle main effects (smaller differences to control formulation), the co-ingredient replacement approach may require more sophisticated statistical techniques and stronger designs (e.g., more replicates, factorial or regression designs, response surface methodology, mixed-effects models, multivariate techniques, simulation modelling, Bayesian hierarchical modelling), as traditional methods (e.g., ANOVA, t tests using three replicates) may lack sufficient statistical power. When adopting co-ingredient replacement in practice, stakeholders including academics, ingredient companies, feed mills and consultants play pivotal roles, each with their unique contributions and challenges. A SWOT analysis—assessing strengths, weaknesses, opportunities and threats—offers a structured approach to understanding these diverse sectors and their intersections in the industry, as shown in Table 1. By examining the components of this analysis, we can examine how the varying attributes and potential strategic pathways for each entity can advance and hinder progress within the field of aquafeed development. Formulation-related environmental outcomes are complex and involve multidimensional trade-offs, which will be outlined in this section. As expected, the choice of formulation approach and environmental standards, and ingredient selection influences these outcomes. Environmental concerns in aquafeed formulation are mostly driven by the selected ingredients and the type of processing required [12]. Life cycle assessment (LCA) tools have been widely used to evaluate the environmental footprint of aquafeeds, offering a comprehensive view of impacts beyond carbon emissions—including water and land use, toxicity and biodiversity [7, 12, 13]. LCA also enables fair allocation of impacts to co-products, supporting circularity and resource efficiency in line with frameworks such as the PEFCR-Feed and the EU Circular Economy Framework. While the carbon footprint remains a central metric, growing attention is being paid to other environmental pressures, revealing trade-offs where low-carbon options may not perform best across all metrics [14]. Notably, fishery-derived ingredients are increasingly recognised as lower-impact alternatives to many agricultural sources [3]. Based on LCA insights (data not shown) for the illustrative formulations presented in Table 2, both strategies show potential to mitigate specific environmental impacts. Co-ingredient replacement tends to offer a more balanced environmental performance across indicators, whereas single-ingredient assessment may yield greater improvements in selected categories but with more significant trade-offs in others (indicator specificity will depend on factors like ingredient sourcing and formulation strategy). Aquaculture nutrition is not only governed by the species requirements and manufacturing logistics but also by social factors. The use of feed ingredients is often subject to debate and is shaped by environmental, ethical and consumer perceptions. Social media has further complicated public perception, often amplifying misinformation and activism that can affect ingredient acceptance [15]. The strategy of co-inclusion of many ingredients may expose the industry to higher public scrutiny when using specific ingredients including genetically modified organisms (GMOs) and their by-products, synthetic additives, wild-caught fishmeal and fish oil, animal by-products and plant ingredients such as soybean meal from deforested regions. Public perception towards these ingredients can vary based on regional laws, regulations, history and culture and the aquaculture industry must navigate these complex social landscapes. Scientific advancements provide opportunities for innovation in feed formulation, but they must also consider societal values and perceptions to gain widespread acceptance. For true progress, the industry must engage in transparent communication and continue research into sustainable and socially acceptable feed ingredients. The feed sector is required to operate under various regulatory frameworks and certification systems that aim to ensure the sustainability and safety of its practices, especially concerning feed ingredients. Policies such as the European Deforestation Regulation (EUDR) and maximum residue limits (MRLs) for feed contaminants set strict boundaries on ingredient sourcing. Certification systems like the Aquaculture Stewardship Council (ASC) Feed Standard v3 [16] also influence ingredient use by imposing constraints on marine and grain ingredient inclusion and sourcing, such as those defined by the MarinTrust v3 standard [17]. Similar restrictions apply to terrestrial ingredients, further complicating feed formulation strategies. Similar to the environmental impacts, adoption of the co-inclusion strategy would require LCA of all ingredients to ensure they adhere to regulatory requirements. Especially for aquaculture producers looking to export their products internationally, adhering to relevant importing countries' certifications and regulations is often necessary. A balanced and strategic application of single-ingredient assessment and co-inclusion formulation approaches can significantly improve the return on investment for R&D. By aligning R&D efforts closely with industrial practices, investment becomes more justified because the results are directly applicable to production. The co-inclusion formulation approach is particularly favourable as it provides feed manufacturers with the flexibility to adjust formulations to minimise cost while reducing the risk of variability between ingredient batches by incorporating a variety of nutrient sources. Furthermore, its focus is multifaceted incorporating synergies and antagonisms amongst ingredients, sustainability metrics, trade-offs related to digestibility, performance and health but also integrates the whole value chain to ensure optimal cost, availability, scalability, regulations and ‘right to play’ for aquaculture producers (i.e., phosphorus or nitrogen from outlet water). On the other hand, the single formulation approach focuses on evaluating the impact of a specific ingredient, offering R&D cost-savings (limited budget and time) and more straightforward responses to communicate. However, this approach has limitations. The application of the findings might be restricted to the exact formulation used during testing, which reduces the broader utility of the research outcomes. As the aquaculture industry expands and faces increasingly complex challenges—including rising ingredient costs, stricter regulatory frameworks and heightened sustainability demands—a shift towards a more comprehensive and well-planned formulation strategy is needed. Both formulation strategies have merit, and their choice should match the research question (Table 3). Co-inclusion offers more practical, flexible and industry-adoptable solutions, while single-ingredient replacement studies are better suited for targeted experiments. To fully realise the potential of co-inclusion formulation for greater impact, future research efforts must focus on refining and validating these methodologies while developing advanced tools for assessing complex ingredient interactions. Strengthening collaboration and transparency amongst stakeholders is essential to keep research relevant and practically applicable, foster more effective resource allocation and support both immediate economic gains and the long-term sustainability of feed development. FCM SPC 0–46 0–20 SBM SFM Corn 41–50 0–10 2.8–3.2 Cricket SBM 0–35 19.5–33.5 SBM PM 15.0–28.5 28.0–45.0 BM Corn PC PBM CPC CGM 1.8–0 7.5–0 8.9–3.9 0–20 10–0 Artur N. Rombenso: conceptualization, writing-original draft preparation, writing review and editing. Brett D. Glencross: conceptualization, writing review and editing. Kyla Zatti: conceptualization, writing review and editing. Helen Ann Hamilton: conceptualization, writing review and editing. Luiz H. David: writing review and editing. Ha H. Truong: conceptualization, writing review and editing. Cedric J. Simon: conceptualization, writing review and editing. The authors declare no conflicts of interest. Artur N. Rombenso is a Senior Research Scientist at CSIRO Bribie Island Research Centre—Australia. He has worked in many areas within aquaculture nutrition (e.g., microbial biomass, insects, oils) and has published continuously in finfish and prawn nutrition. Brett D. Glencross: is a Director of IFFO and Professor at the University of Stirling's Institute of Aquaculture, UK. With extensive expertise in ingredient evaluation and precision nutrition, he explores sustainable ingredient alternatives and digestibility strategies in diverse aquaculture species. Kyla Zatti is a Senior R&D Scientist at BioMar (Trondheim), focusing on optimising marine lipid replacements in salmonid feeds. She holds a PhD in fish nutrition and recently led research demonstrating fish oil replacement with algae oil without compromising growth or taste. Helen Ann Hamilton Global Sustainability Manager at BioMar and holds a PhD in Industrial Ecology. She leads Life Cycle Assessment research—particularly on shrimp feeds—and develops frameworks like BioSustain to analyse aquafeed environmental impacts. Luiz H. David is a Research Scientist at CSIRO Werribee, he focuses on food innovation within aquaculture nutrition, processing novel feed ingredients and improving feed quality and functionality. Ha H. Truong is a Research Scientist and Animal Nutrition Team Leader at CSIRO Bribie Island Research Centre. Her work delves into nutrient digestion dynamics and functional feed additives in finfish and prawn, improving feed efficiency and health. Cedric J. Simon is a Principal Research Scientist and Group Leader at CSIRO Queensland Biosciences Precinct. His research emphasises sustainable feed ingredients, near-infrared spectroscopy for feed composition and microbial additives for finfish and prawn nutrition. The data that support the findings of this study are available from the corresponding author upon reasonable request.