Enzymatic treatment of plant proteins in combination with algae-based nutraceutical inclusion in aquafeeds improves growth performance and physiological traits in the greater amberjack (Seriola dumerili)

Abstract

This study aimed to evaluate, following two different and sequential feeding trials, the effects of partial substitution of fish meal by 44.5 % of plant proteins (similar to 50 % of total protein inclusion) on growth performance, intermediate metabolism, well-being, and muscle chemical composition in the greater amberjack (Seriola dumerili). Additionally, the benefits of performing a previous enzymatic treatment on the plant ingredients before elaborating experimental aquafeeds (Trial II) compared to using untreated plant ingredients were also assessed. Three isoproteic (63 % protein, CP) and isolipidic (18 % crude lipid, CL) diets were used in each experiment: i) a control diet (CTRL), with 75.5 % of protein from marine origin; ii) two experimental diets, with 44.5 % of plant proteins (PP and PPe for Trial I and II, respectively); and iii) the PP/PPe diets supplemented with 3 % of an algaebased functional additive produced by Lifebioencapsulation S.L. (PP-LB and PP-LBe for Trial I and II, respectively). The results showed that using vegetable ingredients enzymatically treated before the production of aquafeed allows the partial substitution of dietary animal marine protein without affecting, or even improving the fish growth performance. The algal-based functional additive did not improve the fish growth when incorporated in plant protein-based diets, although it seems to provide a protective effect to overcome the impairment produced by the first contact of pre-treated vegetalized aquafeeds with the gastrointestinal tract in juvenile amberjack. Moreover, the LB additive could provide other benefits in the long term both in fish fed on diets elaborated with untreated and pre-treated plant ingredients, as evidenced by the level of cortisol released, the protection against oxidative stress, and the improvement in the chemical composition of muscle compared to the fish fed the plant-based diet without the functional additive. These findings demonstrate that the combination of an enzymatic pre-treatment of plant proteins together with the use of nutraceuticals from algae-based additives is a potential tool for more sustainable aquaculture of greater amberjack, a carnivorous species of high commercial interest.