Probiotics enhance resistance to Streptococcus iniae in Nile tilapia (Oreochromis niloticus) reared in biofloc systems.

Biofloc technology is a rearing technique that maintains desired water quality by manipulating carbon and nitrogen and their inherent mixture of organic matter and microbes. Beneficial microorganisms in biofloc systems produce bioactive metabolites that may deter the growth of pathogenic microbes. As little is known about the interaction of biofloc systems and the addition of probiotics, this study focused on this integration to manipulate the microbial community and its interactions within biofloc systems. The present study evaluated two probiotics (B. velezensis AP193 and BiOWiSH FeedBuilder Syn 3) for use in Nile tilapia (Oreochromis niloticus) culture in a biofloc system. Nine independent 3785 L circular tanks were stocked with 120 juveniles (71.4 ± 4.4 g). Tilapia were fed for 16 weeks and randomly assigned three diets: a commercial control diet or a commercial diet top-coated with either AP193 or BiOWiSH FeedBuilder Syn3. At 14 weeks, the fish were challenged with a low dose of Streptococcus iniae (ARS-98-60, 7.2 × 107 CFU mL-1 , via intraperitoneal injection) in a common garden experimental design. At 16 weeks, the fish were challenged with a high dose of S. iniae (6.6 × 108 CFU mL-1 ) in the same manner. At the end of each challenge trial, cumulative per cent mortality, lysozyme activity and expression of 4 genes (il-1ß, il6, il8 and tnfα) from the spleen were measured. In both challenges, the mortalities of the probiotic-fed groups were significantly lower (p < .05) than in the control diet. Although there were some strong trends, probiotic applications did not result in significant immune gene expression changes related to diet during the pre-trial period and following exposure to S. iniae. Nonetheless, overall il6 expression was lower in fish challenged with a high dose of ARS-98-60, while tnfα expression was lower in fish subjected to a lower pathogen dose. Study findings demonstrate the applicability of probiotics as a dietary supplement for tilapia reared in biofloc systems.

Probiotic Treatment Enhances Pre-feeding Larval Development and Early Survival in Zebrafish Danio rerio.

The growth and development of healthy culture subjects are essential in increasing productivity in the aquaculture industry. A primary determinant of aquatic animal productivity is the ambient microbial population. If an aquatic animal's microbiome is diverse, with bacteria favoring beneficial over pathogenic species, the health and growth of the animal (i.e., fish or crustacean) can be substantially improved. Embryonic and newly hatched Zebrafish Danio rerio larvae were reared in the presence of (1) water from the broodstock culture tank as a control, (2) a probiotic solution containing 19 strains of live lactic acid bacteria (LAB), or (3) an antibiotic (AB) solution with amoxycillin. Developmental parameters were monitored until 10 d postfertilization. Bacteria present in the water and larvae were cultured and identified by sequencing the V4 hypervariable region of bacterial 16S ribosomal RNA. Probiotic-treated larvae showed significant increases in every measured morphological parameter and in survival compared to the controls and AB-treated larvae, including TL, eye development, and swim bladder development before first feeding. Staining with DASPEI (2-(4-[dimethylamino]styryl)-N-ethylpyridinium iodide) produced fluorescence, revealing increased mitochondrial activity in the gastrointestinal tracts of probiotic-treated larvae and reflecting advancement of initial metabolic function. Probiotic-treated larvae showed accelerated yolk absorption, resulting in increased nutrient mobilization and growth. Microbial analyses revealed a greater concentration of bacteria in larvae in response to the probiotic treatment compared to the other two treatments. Species identified in all three treatments included Pseudomonas spp. and Aeromonas spp. (Proteobacteria). The second most diverse and abundant microbiome was seen in controls, whereas AB-treated larvae had the least diverse microbiome. All treatments revealed the presence of proteobacteria, but an AB-resistant pathogenic bacterium (Stenotrophomonas maltophilia) was identified in the AB group. These results reveal that the presence of LAB and other bacteria favorably influenced early larval growth, development, digestive function, and survival in Zebrafish even before the onset of feeding.

Probiotics, prebiotics and synbiotics improved the functionality of aquafeed: Upgrading growth, reproduction, immunity and disease resistance in fish.

Aquaculture plays an increasingly significant role in improving the sustainability of global fish production. This sector has been intensified with the advent of new husbandry practices and the development of new technology. However, the increasing intensification and indiscriminate commercialized farming has enhanced the vulnerability of cultivated aquatic species to damage from pathogens. In efforts to confront these various diseases, frequent use of drugs, antibiotics, chemotherapeutics, and agents for sterilization have unintentionally added to the risk of transmission of pathogens and harmful chemical compounds to consumers. Some natural dietary supplements are believed to have the potential to offset this setback in aquaculture. Application of bio-friendly feed additives such as probiotics, prebiotics and synbiotics are becoming popular dietary supplements with the potential to not only improve growth performance, but in some cases can also enhance immune competence and the overall well-being of fish and crustaceans. The present review discusses and summarizes the effects of probiotics, prebiotics and synbiotics application on growth, stress mitigation, microbial composition of intestine, immune system and health condition of aquatic animals in association with existing constraints and future perspectives in aquaculture.