Plant-based feed additives in Cyprinus carpio aquaculture

Species feeding lower at the food web like cyprinids (carp) are often advocated for sustainable aquaculture. However, their gastrointestinal biology (lack of stomach) has limited their acid-peptic digestion, acid lysis of plants and invertebrate tissues, and phosphorus uptake. This review presents data from 118 articles on the use of plant-based feed additives (PFAs) in Cyprinus carpio (common carp). Our review shows that most PFA research in carp is focused on improving feed and nutrient utilization efficiency along various levels (in vivo digestibility, metabolizability to in situ nutrient loading), while other half is focused on ensuring animal welfare standards (biomass, immunity, welfare). Several reviewed plant-based additives however tend to do both. The PFAs include essential oils (EOs), plant-part extracts (PPEs), medicinal plants (herbs) and spices. The effective inclusion rate of EOs is lower (0.5%-0.75%). Whereas PPEs, herbs and spices work at a generic inclusion rate of 2%-5% in carp feeds. Even at an optimum inclusion rate, there are factors controlling PFAs efficacy such as methods of preparation (reviewed). PFAs like lemon beebrush, geranium, dill, Rosemary pepper and common mallow with/without certain pre-conditions are better to avoid in cyprinid diets. Although certain PFAs may potentially alter organoleptic qualities of carp flesh or might assist in training carp immunity, information on these aspects is limited. The review also provides a quick guide to researchers and feed companies interested in exploring the potential of PFAs in C. carpio aquaculture. Potential PFAs that could be valuable for cyprinids, but not yet explored are also listed.