EFFECTS OF SUPPLEMENTING THE FEED TO ATLANTIC COD (GADUS-MORHUA) FRY WITH LACTIC-ACID BACTERIA AND IMMUNOSTIMULATING PEPTIDES DURING A CHALLENGE TRIAL WITH VIBRIO-ANGUILLARUM

Atlantic cod (Gadus morhua) fry were reared on a commercial feed suppl emented with Carnobacterium divergens, isolated from the intestines of Atlantic cod and Atlantic salmon (Salmo salar) alone or in combinatio n with immuno-stimulating peptides. In vitro experiments showed that c ulture filtrates from the isolates from cod and salmon inhibited the g rowth of Vibrio anguillarum. After 3 weeks of feeding, the fish were c hallenged by bath exposure to V. anguillarum (10(7)/ml, 1 h). Twelve d ays after infection significant (p < 0.05) reduced cumulative mortalit y was recorded in fish given feed supplemented with lactic acid bacter ia isolated from Atlantic salmon and with immune-stimulating peptides. No synergistic or cumulative effects were achieved by combining lacti c acid bacteria and immune-stimulating peptides, Four weeks after infe ction the same cumulative mortality (80-84%) was reached in all groups . Both strains of lactic acid bacteria could colonize the internal muc us layer of the cod fry pyloric caeca, and a significant number of the bacteria survived the passage of the whole gastrointestinal tract. (C ) 1998 Elsevier Science B.V. All rights reserved.