The gamma-radiation sensitivity of three kinds of pathogenic bacteria to fish was investigated. D-10 values (irradiation dose required to inactivate 90% of the population) of Edwardsiella tarda, Vibrio anguillarum and Streptococcus faecalis were 0.08, 0.10 and 0.44 kGy, respectively. The inactivation factors were 4.50 - 24.30 and 6.75 - 36.45 at radiation doses of 2 and 3 kGy. Raw moist pellets were inoculated with Edwardsiella tarda, Vibrio anguillarum or Streptococcus faecalis. Inoculated feed samples were packaged in air and irradiated at 5 kGy. This dose was effective in controlling the inoculated and general bacteria in fish feed. We consider gamma-radiation to be an effective method to sterilize pathogenic bacteria in fish feed.
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