AMOXICILLIN IN THE CONTROL OF FURUNCULOSIS IN ATLANTIC SALMON PARR

The efficacy of amoxycillin in the control of laboratory induced Aeromonas salmonicida infection in Atlantic salmon parr was investigated. When given in the diet at a dose rate of 80 mg per kg bodyweight it was effective against both a moderate and severe challenge (with mortality rates in untreated groups of 75 per cent and 45 per cent). At 40 mg per kg it was effective against the moderate challenge only. The plasma levels in these regimes were 1.25-mu-g per ml and 0.3 to 0.6-mu-g per ml and the minimum inhibitory concentration of the challenge strain of A salmonicida was 0.6-mu-g per ml. The potential of the Charm radiobioassay system in detecting antibiotic residues in fish tissue was studied. The level of amoxycillin in muscle and bone from fish in mid-treatment at 80 mg per kg was 0.32-mu-g per ml. After a 12 day withdrawal period at 18-degrees-C no residue was detected within the 0.005-mu-g per ml limit of this test.