Current and Future Approaches to Determining Amino Acid Requirements in Crustaceans

ABSTRACT Nutrition is crucial in aquaculture, with feed ingredients and manufacturing being one of the largest expenditures. The effectiveness of a feed in promoting animal growth and health is dependent on ingredients with appropriate nutritional profiles. Proteins are a costly component of aquaculture feeds; moreover, dietary crude protein requirements for crustaceans can be high, sometimes exceeding 50% of the diet. As proteins are composed of amino acids, understanding species‐specific amino acid requirements is essential for developing cost‐effective, customised commercial feeds. Several methods have been used to determine crustacean amino acid requirements, each with advantages and limitations. Given the varied feeding behaviours between crustacean species, some methods may only be appropriate for certain species. In this review, we propose the Requirements by Ration Level approach as the most suitable method for developing factorial models for feed formulation. This method considers amino acid intake, retention, and loss, whilst integrating digestibility, growth, and chemical composition. It is reliable, accurate, and addresses concerns of amino acid balance changes previously raised in the literature. By using a broken convex curve model instead of a broken line model, more realistic predictions are produced, reflecting dynamic conditions and transitions towards the plateau where the amino acid requirement is met. Additionally, technological advancements have allowed complementary studies in omics, nutritional physiology, and true protein. This review highlights various methods for determining amino acid requirements and demonstrates how the Requirement by Ration Level approach can produce consistent results across experiments, reducing experimental repetition and advancing our understanding of amino acid requirements.