| Summary: | Commercially produced probiotics and prebiotics show potential to enhance growth performance and disease resistance of various animals but have not been evaluated as enrichments in live foods for larval fish. Therefore, four separate trials were conducted to evaluate changes in the production and microbial composition of rotifers (Branchionus plicatilis) exposed to the probiotics Bactocell™ and Aquablend™ and prebiotics Grobiotic®-A, and SILOhealth 108P added to the water during 4-day cultures compared to the control with no supplement. Grobiotic®-A showed potential to increase rotifer production while Bactocell™ decreased production. Denaturing gel gradient electrophoresis (DGGE) analysis demonstrated rotifers cultured with aforementioned additives except SILOhealth 108P altered microbiota composition compared to the control. Bactocell™, a commercial probiotic consisting of Pediococcus acidilactici, has shown benefits to immunomodulation, nutrient digestion, and feed utilization in shrimp but has not been evaluated in fish. Therefore, a feeding trial was conducted with juvenile red drum (Sciaenops ocellatus) fed diets with graded concentrations of Bactocell™ (0, 0.05, 0.1, 0.2, 0.4, and 0.8% of dry weight) for 8 weeks. The diets were formulated primarily from soybean protein sources with low amounts of menhaden fishmeal to contain 44% crude protein and 10% lipid. Each diet was fed to fish in quadruplicate 38-L aquaria for 8 weeks. Digesta from red drum was obtained at the end of weeks 4 and 8 to characterize microbiota by DGGE analysis. Red drum fed experimental diets grew rapidly and achieved a 1,300% increase in initial body weight after 8 weeks; however, no significant (P < 0.05) differences in weight gain, feed efficiency, or survival could be attributed to different concentrations of Bactocell™. After 8 weeks of feeding, DGGE analysis iii showed that Bactocell™ altered the microbiota of red drum digesta compared to fish fed the basal diet. The prebiotics and probiotics tested except SILOhealth 108P ...
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