Dietary Use of Methionine Sources and Bacillus amyloliquefaciens CECT 5940 Influences Growth Performance, Hepatopancreatic Histology, Digestion, Immunity, and Digestive Microbiota of Litopenaeus vannamei Fed Reduced Fishmeal Diets

The accelerated expansion of shrimp farming requires protein sources with high nutritional value to formulate feeds that satisfy shrimp nutritional requirements. Fishmeal (FM) is the main protein source for aquafeed formulations. However, its limited supply and high cost encourage research on alternative protein sources to formulate more profitable feeds that contribute to aquaculture sustainability. Soybean meal (SBM) and poultry by-product meal (PBM) have been used as protein sources for replacing fishmeal, but their essential amino acids imbalance contributes to low shrimp growth performance and affect shrimp health. Therefore, the study purpose was to evaluate the effect of FM replacement by SBM and PBM in diets supplemented with DL-Met, MET-MET (AQUAVI((R))), Bacillus amyloliquefaciens CECT 5940 (ECOBIOL (R)) and their combinations on growth performance and health of juvenile Litopenaeus vannamei. The results showed that FM could be partially replaced with SBM and PBM in shrimp feeds supplemented with 0.19% MET-MET or 0.06% MET-MET plus 0.10% B. amyloliquefaciens CECT 5940 without adversely affecting the growth performance and welfare of Litopenaeus vannamei. These results may be interesting for developing low fishmeal feeds and contributing to aquaculture sustainability. An 8-week feeding trial investigated the effect of Fishmeal (FM) replacement by soybean meal (SBM) and poultry by-product meal (PBM) in diets supplemented with DL-Met, MET-MET (AQUAVI((R))), Bacillus amyloliquefaciens CECT 5940 (ECOBIOL (R)) and their combinations on growth performance and health of juvenile Litopenaeus vannamei. A total of six experimental diets were formulated according to L. vannamei nutritional requirements. A total of 480 shrimp (0.30 +/- 0.04 g) were randomly distributed into 24 tanks (4 repetitions/each diet, 20 shrimp/tank). Shrimp were fed with control diet (CD; 200 g/Kg fishmeal) and five diets with 50% FM replacement supplemented with different methionine sources, probiotic (B. amyloliquefaciens CECT 5940) and their combinations: D1 (0.13% DL-MET), D2 (0.06% MET-MET), D3 (0.19% MET-MET), D4 (0.13% DL-MET plus 0.10% B. amyloliquefaciens CECT 5940 and D5 (0.06% MET-MET plus 0.10% B. amyloliquefaciens CECT 5940). Shrimp fed D3 and D5 had significantly higher final, weekly weight gain, and final biomass compared to shrimp fed CD (p < 0.05). Shrimp fed D2 to D5 increased the hepatopancreas epithelial cell height (p < 0.05). Digestive enzymatic activities were significantly increased in shrimp hepatopancreas' fed D3 (p < 0.05). Meanwhile, shrimp fed D1 had significant downregulation of immune-related genes (p < 0.05). Moreover, shrimp fed D3 and D5 increased the abundance of beneficial prokaryotic microorganisms such as Pseudoalteromonas and Demequina related to carbohydrate metabolism and immune stimulation. Also, shrimp fed D3 and D5 increased the abundance of beneficial eukaryotic microorganism as Aurantiochytrium and Aplanochytrium were related to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production which plays a role in growth promoting or boosting the immunity of aquatic organisms. Therefore, fishmeal could be partially substituted up to 50% by SBM and PBM in diets supplemented with 0.19% MET-MET (AQUAVI((R))) or 0.06% MET-MET (AQUAVI((R))) plus 0.10% B. amyloliquefaciens CECT 5940 (ECOBIOL (R)) and improve the productive performance, health, and immunity of white shrimp. Further research is necessary to investigate synergistic effects of amino acids and probiotics in farmed shrimp diets, as well as to evaluate how SBM and PBM influence the fatty acid composition of reduced fishmeal diets and shrimp muscle quality. Nevertheless, this information could be interesting to develop low fishmeal feeds for aquaculture without affecting the growth and welfare of aquatic organisms.