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 aquaculture 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 microbial balance. In the present study a dry feed containing lactic acid bacteria (Carnobacterium divergens) isolated from Atlantic cod (Gadus morhua) 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 acid bacteria supplemented feed. A certain improvement of disease resistance was obtained, and at the end of the experiment lactic acid bacteria dominated the intestinal flora in surviving fish given feed supplemented with lactic acid bacteria. No obvious growth inhibition of V. anguillarum was observed in an in vitro mixed culture of this bacterium and the C. divergens isolated from cod intestines.