Evaluation of Commercial Prebiotic and Probiotic Diet Additives on Growth Performance, Stress Response, and Immunity of Hybrid Striped Bass (Morone chrysops × M. saxatilis)

Abstract

Aquaculture is a fast-growing industry on a global scale in which the use of antibiotics and chemotherapeutics are being discouraged. Prebiotic and probiotic supplements are promising antibiotic alternatives that may aid in health enhancement and disease prevention. An outdoor pond trial evaluated commercial prebiotic (GroBiotic®-A) and probiotic (Aquablend®) products under conditions simulating commercial aquaculture. Juvenile hybrid striped bass with mean initial weights of 77 g were fed in triplicate ponds for 11 months with diets containing either 0 or 2% of the prebiotic and 0 or 10^7 CFU g^-1 of the probiotic in a factorial arrangement. Although growth performance was unaffected by experimental diets, both supplements resulted in elevated innate immune responses and longer intestinal fold length indicating potential improvements in health. Microbiome results did not suggest significant differences in transient microbiota diversity among diets. The effects of supplements on stress responses of hybrid striped bass were investigated through two additional experiments. Cage-raised hybrid striped bass averaging 429 g were subjected to handling and confinement stress after being fed the prebiotic- and probiotic-supplemented diets for 12 months. A second stress challenge trial was designed to verify survival results and monitored hematological stress responses. Results showed that the commercial prebiotic and probiotic supplements altered the physiological responses of acute stress and have the potential to improve post-stress survival of hybrid striped bass. An additional 15-week laboratory trial was conducted with fingerling hybrid striped bass in a recirculating system to characterize effects of the additives over time. Fingerlings fed the supplements had better growth overall but only displayed statistical differences at weeks 3, 4, and 5. At every sampling time, bacterial composition of lumen transient bacteria differed significantly from that of the mucus-colonized bacteria in all treatments. At weeks 4 and 8, there were no significant differences in bacteria composition among dietary treatments. A water quality challenge following the feeding trial suggested improved survival by supplementation of the additives. It is concluded that performance of the prebiotic and probiotic products in largescale production partially agreed with previous laboratory results and have potential to enhance the overall health of hybrid striped bass.