Deconstructing the Fish Meal and Fish Oil Replacement Story in Aquaculture: Focusing on Nutrient Requirements, Characterization of Feed Ingredients and Pragmatic Approaches

Fish meal and fish oil replacement has been the focus of very significant research efforts and hundreds ofscientific papersin recent years.Despite years of research, fish meal and fish oil remain very important, quasi essential, components of successful commercial feeds for most fish and crustacean species. This generally has an impact on the feed and production costsformany aquaculture products.

The potential to reduce level of fish meal and fish oil in aquaculture feedsis linked with our potential to improve the wholesomeness of our understanding of this issue. Unfortunately, much of research efforts invested so far have had shallow focus and/orinadequate design. Aquaculture nutrition researchers tend to forget that "fish meal and fish oil replacement" is not a true research objective in itself and that fish meals and fish oils are complex ingredients with highly variable chemical compositions and nutritive values.

Research and development (R&D) efforts should ideally be a lot more pragmatic and no longer be focused on the "replacement" of one ingredient by other ingredients but rather on "what the animal requires" and "how can we cost-effectively and safely meet the requirements of the animals". Progress is therefore highly dependent on a "balanced" understanding of the nutritional requirements of the animals and the chemical composition and nutritive value of different feed ingredients and feed additives.

Over the past five decades, dozens of different protein and lipid sources have been evaluated in hundreds of “practical” feeding trials. Many of these trials focused on replacing fish meal, fish oil or other high quality protein and lipid sources by putatively more cost-effective protein and lipid sources. What is often overlooked in many trials is that fish meals and fish oils are complex ingredients that are known to vary greatly in chemical composition. The raw material sources and types, seasons, and processing equipment and conditions used in the manufacturing of these ingredients all have great impacts on the chemical composition and nutritive value of these ingredients. Incorporation "20% fish meal in the diet" or "replacing 50% of the fish meal or fish oil of the diet" may mean very different things depending on the type and chemical composition of the fish meal and fish oil used in the study and the fish meal and fish oil levelsin the control diet.

In many feeding trials, the control diet is formulated with high fish meal levels and/or all essential nutrients are supplied greatly in excess of requirements. The test ingredient is included at graded levels and effect on growth performance is monitored. Under these conditions, the evaluation of the nutritive value of the “test” ingredients is not very robust nor is it specific enough. For example, a certain level (e.g. 20%) of the test ingredient may be observed to support optimal growth performance in feeds formulated to very high essential amino acid levels (e.g. high fish meal feeds). However, the same level of test ingredient may not be suitable for feeds formulated with low fish meal level and/or lower essential nutrient levels.

There is a need to refine methodological approaches so that the focus is on assessment of available nutrient “contribution” of ingredients to the diet (i.e. the bioavailability of nutrients in ingredients) rather than “absence of effect” of test ingredients. Studies focusing on the quality and "bio-available" nutrient contribution of feed ingredients have been relatively few and far between. To date assessment of the nutritional value of ingredients has mainly focused on apparent digestibility of proximate analysis components (dry matter, crude protein, lipid, gross energy) and much less emphasis on specific nutrients, with exception of a few key nutrients (e.g., lysine, methionine, phosphorus). There is a need for detailed and accurate characterization of the bio-availability of nutrients in common feed ingredients, the variability in composition and bioavailability of nutrients within ingredient and the various factors (e.g. dietary interactions, biotic factors) that may affect the bioavailability of nutrients in complete feeds.

The characterization of the fine chemical composition of different feed ingredients and feed additives should become a priority. Attention should be especially paid to the nutrients and other chemical components present in fish meals, fish oils and other animal products, notably those that may be absent or only at low levels in ingredients of plant origins. R&D efforts should not only focus on the traditional essential nutrients (e.g., essential amino acids, essential fatty acids, minerals, vitamins) but also on more minor nutrients which may play importantroles under certain conditions or be conditionally essential at certain life stages(e.g. phospholipids, nucleotides, carotenoids, etc.).

Significant efforts have also been invested over the past five decades on the definition of the nutrient requirements of different fish and crustacean species. Despite the thousands of studies published on this topic, it is becoming clear that state-of-the-art is less advanced than what is required by the aquaculture feed industry. A comprehensive review of the literature carried out by an international committee of experts appointed by the US National Research Council to review the nutritional requirements of fish and shrimp recently identified several significant gaps in the definition of nutritional requirements for most commercially important species (NRC, 2011).Globally, there is also need for significant improvements in the focus of studies, the scope and quality of the experimental design and methodological approaches used, and the characterization of the diets and ingredients used. Overall, more systematic efforts need to be invested. It would be recommendable to increasingly focus the research efforts on the 15 or so fish and crustacean species (e.g., carp species,, tilapias, Pangasid catfish, Atlantic salmon, Penaeid shrimp, etc.) that represent more 80% of the global farmed fish and crustacean production.

While improving the accuracy of estimates of essential nutrient requirements and improving the characterization of feed ingredients are critical factors, determining how this information can be translated into meaningful and robust nutritional and feed formulation guidelines is equally important. It is a very complicated issue that is too often overlooked by aquaculture nutritionists.

Aquaculture feeds are characterized by the wide nutritional specification to which they are formulated to. This is expected given the very large number of fish and crustacean species produced around the world using feed-based production systems. However, the protein, lipid, starch and digestible energy contents of feeds can significantly vary not only as a function of species and life stages for which they are formulated (trout vs. tilapia feed, starter vs. grower vs. finisher feed), but also as a function of a myriad of other factors, such as production systems, farmers' or feed manufacturers’ preferences, environmental constraints, and socio-economical conditions (e.g., fish price, access to credit, degree of risk). Most fish feed manufacturers have to serve a large client base cultivating numerous fish and invertebrate species in very different production systems (ponds vs. cages, marine vs. freshwater environment, etc.) and socio-economical contexts (small farmers vs. large vertically integrated corporations).

These factors, as well as, the multitude of opinions with regards to optimal levels and modes of expression of essential nutrient requirements limits the ability of manufacturers to meaningfully translate scientific advances into practical and cost-effective feed formulation guidelines. There is clearly a need for more consideration of how the information may be potentially used when designing research trials.

Contrasting the response of animal to increasing essential nutrient levels in different dietary matrices (e.g. diets with different digestible energy levels), and different species and life stages may allow to gain knowledge on the impacts of these different factors on essential nutrient utilization and requirements and enable the development of more robust feed formulation guidelines and models.

In defining the focus and objectives of R&D efforts, aquaculture nutrition researchers and feed manufacturers should keep the perspectives of aquaculture producers in mind. They ideally should first focus on generating information needed to meaningfully address key economical and production issues (growth, feed efficiency, disease resistance, product quality, etc.). The focus also should be on generating information needed to be able to adapt feed formulations to an ever more competitive and demanding market and to stricter environmental constraints and consumer demands.

Increasing collaboration between feed manufacturers, ingredient suppliers, fish producers, and research organizations has been instrumental in improving the quality and relevance of fish nutrition research in the past few decades. Many aquaculture feed manufacturers are investing heavily in research and development activities and have established own research facilities to test their commercial feed formulations, determine the effect of feed composition/nutritional specifications and feed ingredients on growth and feed efficiency of animals grown under commercial-like conditions. This has probably resulted in improvement of the quality of feed available to aquaculture producers. However, limited amount of information from these efforts trickles down to the global aquaculture nutrition community since the information generated is generally proprietary and is closely guarded from public disclosure for competitive advantage. Nonetheless, a healthy, arm-length, relationship with different industry stakeholders can truly help commercial relevance of academic research efforts in aquaculture nutritionand help this field meaningfully progress to address current and future challenges, including those related to fish meal and fish oil replacement.