ISSUE FOCUS FEED & ADDITIVE MAGAZINE September 2022 27 MCFA as a control. Clear rings (inhibition zones) were observed in all concentrations. Respective to the doses, the radii of clear rings were 6, 8, 10, 12, and 15 mm for V. alginolyticus and 7, 8, 12, 14, and 16 mm for V. harveyi (Figure 1). The bacteriostatic effect of the MCFAs on V. parahaemolyticus was also evaluated with a standard minimal inhibition concentration (MIC) test. On a medium with a pH adjusted to 7.0, the optical density (OD) of bacterial cultures were incubated for 24 hours. Different concentrations of the MCFA were then measured. At a concentration of 0.1%, the OD was statistically similar to the blank control. Therefore, this concentration can be considered as the minimal inhibition concentration for V. parahaemolyticus. ANTIMICROBIAL ACTIVITY AGAINST BACTERIAL AND VIRAL PATHOGENS The MCFAs C6, C8, C10, and C12 were tested on common aquatic bacterial pathogens and found to complement each other and work synergistically to inhibit bacterial growth. It was found that C8 and C10 are more effective against gramnegative bacteria—such as Vibrio, Aeromonas, and Edwardsiella—while C10 and C12 are more effective against gram-positive bacteria like Streptococcus and Staphylococcus (Figure 2). Figure 1. Clear inhibitory zones showing effect of MCFAs on (A) V. alginolyticus and (B) V. harveyi Supplant D Health and performance go hand in hand • Inhibits bioluminescent vibrio, other pathogenic bacteria and WSV • Improves gut and hepatopancreas morphology • Minimizes injury to hepatopancreas agrimprove.com Aromabiotic® Aqua
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