Dietary Supplementation of a Commercial Prebiotic, Probiotic and Their Combination Affected Growth Performance and Transient Intestinal Microbiota of Red Drum (Sciaenops ocellatus L.)

SIMPLE SUMMARY: Feeds for farmed fish containing high levels of plant ingredients and high stocking densities can impact the marine carnivorous fish growth and impair their intestinal health status, which ultimately leads to an increased infection susceptibility. To mitigate these negative impacts, feed additives such as live bacteria (probiotics), and complex fibers to induce the growth of beneficial bacteria in the intestine (prebiotics), have been successfully supplemented to the diets of different fish species, including the red drum. This is the first report to date exploring potential synergisms between prebiotic and probiotic for this important marine fish species. Our results show that these additives in low fishmeal-based diets can improve growth performance and modify the protein composition of red drum juveniles. Their transient intestinal bacterial community was also modulated, by reducing the abundance of possible pathogenic bacteria responsible for considerable losses in intensive aquaculture systems. These findings are important steps towards more sustainable aquaculture practices and environmentally oriented aquafeed formulations. ABSTRACT: In the present study, the potential synergism between beneficial lactic acid bacteria (Pediococcus acidilactici) contained in a probiotic and a mixture of fermentable complex carbohydrates and autolyzed brewer’s yeast (or prebiotic) were explored in red drum. Four experimental diets were formulated from practical ingredients, and the basal diet was supplemented with either probiotic, prebiotic, or both supplements. Red drum juveniles (~5.5 g) were offered the four experimental diets for 56 days, and at the end of the feeding trial fish fed diets supplemented with probiotic had significantly better weight gain than those fed the non-supplemented diets, and higher protein content in their whole-body composition. Transient intestinal microbiome alpha and beta diversity were significantly affected by the dietary treatments. Interestingly, a higher relative abundance of the lactic acid genus Pediococcus was observed for fish fed diets supplemented with the prebiotic. A higher relative abundance was also observed for the predicted functions of the microbial metagenome, and many of these pathways involved the biosynthesis of essential amino acids, vitamins, and nucleotides. Even though no potential synergistic effect was observed, the individual inclusion of these prebiotic and probiotic supplements positively affected the intestinal health and growth performance of red drum, respectively.