PROBIOTIC EFFECT OF LACTIC-ACID BACTERIA IN THE FEED ON GROWTH AND SURVIVAL OF FRY OF ATLANTIC COD (GADUS-MORHUA)

A growing concern for the high consumption of antibiotics in aquacultu re has initiated a search for alternative methods of disease control. Improved resistance against infectious diseases can be achieved by the use of probiotics. Probiotics are live microorganisms supplemented in food or feed which give beneficial effects on the intestinal microbia l balance. In the present study a dry feed containing lactic acid bact eria (Carnobacterium divergens) isolated from Atlantic cod (Gadus morh ua) intestines was given to cod fry. After three weeks of feeding the fry was exposed to a virulent strain of Vibrio anguillarum. The death rate was recorded during further three weeks of feeding with lactic ac id bacteria supplemented feed. A certain improvement of disease resist ance was obtained, and at the end of the experiment lactic acid bacter ia dominated the intestinal flora in surviving fish given feed supplem ented with lactic acid bacteria. No obvious growth inhibition of V. an guillarum was observed in an in vitro mixed culture of this bacterium and the C. divergens isolated from cod intestines.