Journal of Aquaculture Research & Development

Abstract

Probiotic and Pathogen Ex-vivo Exposure of Atlantic Salmon (Salmo Salar L.) Intestine from Fish Fed Four Different Protein Sources

Mali Hartviksen, Jose L Gonzalez Vecino, Anu Kettunen, Reidar Myklebust, Kari Ruohonen, Simon Wadsworth and Einar Ringø

The present study addressed the adherence of Carnobacterium divergens and Aeromonas salmonicida subsp. salmonicida to the intestinal lining of Atlantic salmon (Salmo salar L.) using an ex vivo method–intestinal sacfollowing feeding with pea protein concentrate, extracted sunflower or feather meal at 200 g/kg inclusion level. Control diet was a 450 g/kg fishmeal diet. The experimental feeds were fed to two groups each for seven weeks at EWOS Innovations’ facilities in Lønningdal, Norway. Ex vivo intestinal challenge was carried out at Institute for Marine Research, Bergen. Excised intestines of salmon from all feeding groups were exposed to a probiotic, C. divergens or a pathogen, A. salmonicida either alone or in combination and control samples were exposed to sterile saline solution. Exposure to A. salmonicida caused severe damage to the intestinal ultrastructure of the mid intestine, but after exposure to C. divergens, sterile saline solution or any of the combination treatments, morphology remained mostly unaltered indicating an alleviating effect of the probiotic. Feather meal intensified the damaging effect of exposure to A. salmonicida and there were otherwise no effect of diet on the morphology. qPCR analysis of adhered C. divergens and A. salmonicida showed that although the pathogen has a higher adherence efficiency, C. divergens was more efficient at displacing the pathogen if allowed to adhere to the mucosal lining first indicating that the probiotic should be present prior to the pathogen for optimal effect. There were no dietary effects on bacterial adherence. The present study shows that use of some commercially available alternative feed ingredients may not affect the probiotic abilities of C. divergens or make the fish more susceptible to disease through intestinal invasion.