The botanical product evaluated in this study represents an innovative and sustainable formulation as an alternative to the use of antibiotics in aquaculture. Its combination of organic acids and plant extracts has demonstrated effective antimicrobial properties, as well as supporting fish welfare, ensuring the quality of the final product and reducing the risk of bacterial resistance.
To evaluate its effectiveness, the administration of Florfenicol at 20 mg/kg for 10 days was compared with a reduced dose of Florfenicol (10 mg/kg) combined with the natural product, in Atlantic salmon (Salmo salar) experimentally infected with Piscirickettsia salmonis. The challenge was performed by intraperitoneal inoculation using two genetically distinct strains: LF-89 and EM-90, recognized for their difference in virulence and pathological patterns. Variables such as mortality, bacterial load, immunological parameters and histopathological indicators were evaluated.
Histopathological analyses revealed that the LF-89 strain predominantly produces kidney and liver lesions, while EM-90 generates a more systemic effect, with hemorrhages in multiple organs. Variables such as mortality, immunological markers, bacterial load and general health indicators were evaluated.
During the test, the fish maintained an intake greater than 1.5% of their body weight and no relevant biometric alterations were observed. Clinical signs appeared between days 20 and 26 post-inoculation in the positive control group, with a cumulative mortality of 40% at day 37. In contrast, both the botanical + Florfenicol combination and Florfenicol alone reduced mortality to 6.7%, equaling the negative control.
Both treatments also achieved a significant reduction in bacterial load. The combination with the botanical product at half dose of the antibiotic obtained an efficacy comparable to treatment with Florfenicol at full dose. This suggests a synergistic action that enhances the effect of the antibiotic and stimulates the immune system. Complementing these results, a field study conducted on Oncorhynchus kisutch showed that the exclusive use of the botanical product significantly decreased the scores of oxidative stress, inflammation and deficient immunocompetence. In addition, better integrity of the skin, fins and mucus, as well as a reduction in external injuries.
In conclusion, the botanical product presents a promising and sustainable approach to the control of Piscirickettsia salmonis in Atlantic salmon, allowing to reduce the use of antibiotics by up to 50% without compromising the efficacy of the treatment.