Alternative protein sources in aquafeed: Current scenario and future perspectives

Fish meal represents the main protein source for most commercially farmed aquatic species, as it is characterized by high nutritional value and lack of anti-nutritional factors. However, its availability and the market price have been recognized as serious problems at least for over a decade, making it necessary to search for non- conventional protein sources, as an alternative to fish meals. This review aims to comprehensively examine and critically revise the use of fish meal and all alternative protein sources explored to date on the health, welfare, and growth performance of the major aquatic species commercially interesting from a global scenario. The investigation revealed that the inclusion levels of the different protein sources, plant- and animal-derived, ranged from 10 to 80 % and from 2 to 100 % respectively, in partial or complete replacement of fish meal, and generated positive effects on health, welfare, growth performance, and fillet quality. However, the results showed that above a certain level of inclusion, each protein source can negatively affect fish growth performance, metabolic activities, and other biological parameters. Moreover, it is likely that by mixing different protein sources, the combination of each ingredient causes a synergistic effect on the nutritional properties. Therefore, the future of aquatic feed formulation is expected to be based on the blend of different protein sources. Overall, the analysis highlighted the need for additional research in the field of replacing fish meals with new protein sources, given that many knowledge gaps are still to be filled on aquatic species, which deserve to be investigated.