Comparing Methionine Synthetic Sources: Supplementation of Aquafeeds, Bioefficacy, and Effects on Finfish Oxidative Status

ABSTRACT The shift from fishmeal‐based diets to diets including alternative ingredients to improve the sustainability of the aquaculture industry is necessary. Still, it entails numerous challenges, including balancing the dietary essential amino acids, as alternative ingredients, such as plant proteins, insect meals, single‐cell proteins, or animal by‐products, are usually deficient in some amino acids, particularly methionine (Met). Besides being required for protein synthesis and maintenance purposes, Met serves as a methyl donor. It plays an important role in the antioxidant system through its downstream metabolites, for example, glutathione and taurine. In practical diets, the requirements of animals are fulfilled from three primary sources: L‐Met (the natural form of Met), DL‐Met, and DL‐hydroxy‐Met (OH‐Met). Dispersed literature data are available on the efficiency of using these dietary Met sources in aquaculture finfish species. This review intends to compare the efficacy of the different dietary Met sources in finfish growth and their potential role in the antioxidant defense system.