Using probiotic additives has proven to be a promising prophylactic measure for diseases caused by bacterial agents in aquaculture, in order to minimize the inappropriate and illegal use of antimicrobials, in addition to promoting greater productive performance in fish. However, there is no scientific literature regarding the use of autochthonous probiotic bacteria for rearing B. amazonicus, and their benefits are unknown; fish specie with commercial importance nationally and in Latin America. The objective of this study was to evaluate the effect of probiotic bacterial strains of yamú on its growth performance and resistance to infection by Aeromonas jandei.
Yamú juveniles (N= 220) weighing 64.8 ± 10.36 g were kept in experimental boxes (310 L) under controlled conditions. Were randomly distributed in 20 boxes, divided into three treatments plus the control group, with five replicates per group. Bacterial strains were isolated from the intestines of healthy yamús, identified, and characterized in vitro. They were freeze-dried and tested in combination with each other (1:1 ratio), with T1= B.pumilus:L.plantarum:L.sphaericus; T2= B.cereus:B.megaterium:L.lactis; T3= mix of the six strains mentioned previously; and Control= commercial feed without probiotics. The base diet was commercial feed (NUTRIPISCIS- PRESENCE®, 36% CB), and bacterial freeze-dried foods were added to the feed with soybean oil (2%) in a proportion of 10 g of probiotics for every 1 kg of feed. The animals were fed 3% of their body weight twice daily for 60 d. At the end of the experiment, all animals were assessed to determine zootechnical parameters. Then, 20 fish per treatment were challenged against the pathogenic strain A. jandei (2.4 x 108 CFU mL-1 of live bacteria; 0.1 mL inoculum for every 10 g of fish injected intraperitoneally) and evaluated for disease resistance.
All collected data were statistically analyzed using one-way analysis of variance (ANOVA) and Tukey’s mean comparison test (p < 0.05). Infection resistance data were assessed using Kaplan–Meier survival analysis (S%). The performance parameters, i.e., total final weight (FW), weight gain (WG), and relative growth rate (RGR) showed no statistical differences between probiotic treatments or when compared with the control. There was no significant difference in bacterial resistance between treatments (Table 1).
Although they are species-specific strains, never studied in in vivo tests, the treatments did not demonstrate productive or health benefits as a food additive for yamú in the juvenile phase. The isolation and selection of autochthonous strains is still an ambiguous and comprehensive area in aquaculture, especially in native species. However, its strategic use in other production phases can be a key to its success and development of new inputs for fish farming.
Financial support: Research Support Foundation in the State of Amazonas (FAPEAM).