Aquafeed Vol 14 Issue 3 2022

Page 14


Optimizing efficiency and lowering aquafeed costs using the ideal protein concept Ewen McLean, Kelly B. Alfrey, Delbert M. Gatlin III, T. Gibson Gaylord, Frederick T. Barrows A new analysis of the essential amino acids (EAA) of ten major farm-raised fish and shrimp species can help the industry drive down the cost of aquaculture feeds and make them more efficient. To our knowledge, this analysis is the first to examine such a wide variety of species' EAA using the same laboratory. The analysis of EAA was motivated by the ideal protein concept (IPC) that advocates optimizing the blend of essential amino acids in feeds to precisely meet the target animal’s requirements for growth and maintenance. An animal’s EAA profile is considered to reflect an optimal blend for dietary EAAs. For over 50 years, swine and chicken feeds have been formulated with the IPC philosophy. The goal is a more efficient feed, in terms of cost, decreased waste and pollution, including nitrogen excretion. Fishmeal has long been included in aquafeeds due to its favorable amino acid profile which closely resembles that of its consumers. However, with scarcity in wild-caught fish driving fishmeal prices higher, the IPC has gained momentum in aquafeed formulation over the last several years with the arrival of new and innovative protein sources, such as single-cell proteins and insect meals that offer a greatly expanded ingredient pantry for research and development. By focusing on matching animal and feed EAA profiles, feed formulators can create more efficient formulations using less expensive ingredients. Understanding EAA requirements is critical to formulating cost-efficient feeds. And yet, of the over 230 species of aquatic animals currently being aquacultured, the complete EAA requirements are known for only a handful of them. When an animal’s nutritional requirements are unknown, the EAA analysis provides a good starting point to optimize that animal’s feed. The IPC relies on knowing the quantitative requirements of a reference EAA. Because Lysine (Lys) is one of the first limiting amino acids and its analysis is uncomplicated, it is often the first analyzed. All other requirements for EAA can then be expressed as a percentage of Lys.

In our recent study published in Aquaculture and Fisheries, we evaluated EAA muscle profiles of commercially important species, such as largemouth bass (Micropterus salmoides), channel catfish (Ictalurus punctatus), grass carp (Ctenopharyngodon Idella), Nile tilapia (Oreochromis niloticus), red drum (Sciaenops ocellatus), pompano (Trachinotus carolinus), longfin yellowtail (Seriola rivoliana), Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), yellowfin tuna (Thunnus albacares) and Pacific whiteleg shrimp (Litopenaeus vannamei), which represent nine orders. The analyses were conducted by the same lab to eliminate variation due to lab technique so that differences in EAA could be detected across species, facilitating the efficient formulation of feed that mirrors the EAA muscle requirements. In the fish group, little difference in EAA ratios (the A/E ratio) among the 10 species was detected and Lys represented the dominant muscle EAA measured, ranging between 7.06 and 9.58 g/100 g protein. However, distinct differences were seen between the EAA of whiteleg shrimp and fish. For the shrimp, arginine (Arg) was the principal EAA followed by Lys. Good correlations have been found between wholebody and muscle EAA profiles. Further requirements have been estimated using the A/E ratio. The A/E ratio does not provide the quantitative requirement for EAAs but the relative balance among the ten EAAs. Preparing feeds with this exact balance provides the means of creating low-protein feeds that return identical performance, in terms of growth rates and feed conversion ratio, when compared to an unbalanced, high-protein feed. IPC also reduces feed costs since proteins are one of the most expensive nutrients in feed, and feed is one of the most expensive variable costs in aquaculture production. Therefore, the more efficient the feed, the more profitable and more sustainable aquaculture can become. This study offers a good starting point to better formulate aquafeeds to minimize costs and maximize efficiency.

The study was supported by the F3 – Future of Fish Feed’s Feed Innovation Network. Aquafeed: Advances in Processing & Formulation Vol 14 Issue 3 2022

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