Tracing the Trophic Fate of Aquafeed Macronutrients With Carbon Isotope Ratios of Amino Acids

To meet future seafood demands, ingredients derived from algae and other novel and sustainable sources are increasingly being tested and used as replacers to traditional aquafeed ingredients. Algal ingredients in particular are being promoted for their sustainability and their additional functional attributes in farmed aquatic animals. Test on algal supplemented aquafeeds typically focus on a suite of immunological and physiological indicators along with fish growth performance or muscle quality. However, to optimize the replacement of fish meal with algal derived ingredients, it is crucial to understand the metabolic fate in the algal macronutrients (carbohydrates, fats, and proteins), and their nutritional interactions with other ingredients after ingestion. Here, we assess the potential of using the emerging technology- stable carbon isotope (delta C-13) analysis of single amino acids (AAs) as a nutritional biomarker in aquaculture. Applications of delta C-13(AA)-based approaches in feeding trials show promise in closing the knowledge gap in terms of understanding how fish and other aquaculture taxa assimilate and metabolize algal derived macronutrients. Source diagnostic delta C-13 fingerprints among the essential AAs can trace the protein origins to broad phylogenetic groups such as red macroalgae, brown macroalgae, bacteria, and terrestrial plants. Among the non-essential AAs, delta C-13 patterns have the potential to inform about metabolic routing and utilization of dietary lipids and carbohydrates. Despite the potential of delta C-13(AA) as a nutritional biomarker, the few applications to date in fish feeding trials warrant further development and implementation of delta C-13(AA)-based approaches to improve understanding of protein origins and macronutrient metabolic routing.

Automated summary

To meet future seafood demands, researchers are exploring the use of ingredients derived from algae and other sustainable sources as replacers for traditional aquafeed ingredients. Algal ingredients are being promoted for their sustainability and additional functional attributes in farmed aquatic animals. Stable carbon isotope analysis of single amino acids (AAs) shows promise as a nutritional biomarker in aquaculture to understand the digestion and metabolism of algal macronutrients. Although there have been few applications to date, there is potential for further development and implementation of delta C-13(AA)-based approaches to improve understanding of protein origins and macronutrient metabolic routing.