DIETARY INCLUSION OF A Saccharomyces cervisiae FERMENTATION PRODUCT TO A COMMERCIAL RATION IMPROVES IMMUNE READINESS AND COLUMNARIS DISEASE RESISTANCE IN HYBRID CATFISH Ictalurus punctatus X Ictalurus furcatus

Benjamin H. Beck*, Rashida Eljack, Mediha Aksoy, and Eric Peatman
 
*United States Department of Agriculture-Agricultural Research Service
Aquatic Animal Health Research Unit
990 Wire Road, Auburn, AL, 36832
benjamin.beck@ars.usda.gov

Columnaris disease, caused by Flavobacterium columnare, continues to be one of the most detrimental bacterial diseases of catfish commercially grown in the US.  There are currently few effective weapons available to combat this disease.  Catfish producers are eager to gain protection against disease in a more natural and cost-effective manner, i.e. through a diet supplemented to provide for mucosal health as well as performance.  In the present study, we evaluated a Saccharomyces cerevisiae fermentation product called Diamond V XPC.  The trial featured four levels of XPC at rates of 0, 2.5, 5, and 10 lb per ton which were added to a commercial 32% protein floating catfish ration.  Following six weeks of feeding, there were no differences in growth except in fish fed the 5 lb/ton dose, which were significantly larger (80.7 + 1.6 g) than control fish (75.2 + 2.2 g) at the end of the 6 week trial (P<0.05).  There were no significant differences between the feed conversion ratios (FCR) of any treatment.  Hematological analyses revealed differences in the cellular composition of the blood in XPC fed animals as compared to the control group.  White blood cell numbers were significantly higher (P<0.001) in the 5 and 10 lb/ton treatment.  Differences were also evident in the red cell compartment, with the absolute number of red blood cells being significantly greater in the 2.5 and 5 lb/ton treatments.  At the end of the feeding trial an F. columnare challenge was performed to examine the influence of Diamond V XPC on columnaris disease susceptibility.  The challenge revealed that animals fed XPC showed significantly better survival; however, the overall mortality was relatively low with 16.3%, 0%, 0%, and 1.25% mortality observed in the 0, 2.5, 5, and 10 lb/ton treatments respectively.  Trials are ongoing to repeat this work in channel catfish Ictalurus punctatus.