Probiotic Feeding Experiments with Juvenile Channel Catfish and Nile Tilapia

Authors: Shelby, Richard; Lim, Chhorn; Aksoy, Mediha; Klesius, Phillip

Submitted to: Aquaculture Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/5/2007
Publication Date: 2/26/2007
Citation: Shelby, R.A., Lim, C.E., Aksoy, M., Klesius, P.H. 2007. Probiotic Feeding Experiments with Juvenile Channel Catfish and Nile Tilapia. Aquaculture Conference Proceedings. Aquaculture 2007. February 26 - March 2, 2007 San Antonio , Texas. p. 842.

Interpretive Summary:

Technical Abstract: Probiotic microbial feed supplements are gaining wide acceptance in livestock production, and may be applicable to aquaculture production systems. We have conducted a series of experiments using commercial probiotics added to diets of juvenile channel catfish, Ictalurus punctatus (Rafinesque), and Nile tilapia, Oreochromis niloticus, to determine if there are beneficial effects with regard to weight gain and disease resistance. Commercial probiotics, singly and in combination, were incorporated into a commercial diet fed to juvenile channel catfish in aquaria. Microbial analyses were conducted to confirm viability of the bacteria under storage conditions. Fish were fed twice daily to apparent satiation and weighed biweekly for 8 weeks. Protein, immunoglobulin, complement, and lysozyme analyses were conducted. Disease resistance was determined in the remaining fish by observing mortality caused by Edwardsiella ictaluri after immersion challenge. Specific antibody was measured by ELISA in the fish which survived challenge at 15 days. The viable probiotics would be recovered at between 10 to the sixth power and 10 to the seventh power colony forming units per gram (CFU/g) of diet after storage at 5 degrees C for 4 weeks. No significant differences in levels of protein, immunoglobulin, complement, or lysozyme were noted between fish consuming probiotic diets or the control diet. In one feeding trial, weight gain per fish was significantly less in the fish receiving a combination of Pediococcus and Enterococcus probiotic bacteria when compared to those consuming either bacterial supplement diet alone or the control diet. We conclude that these particular commercial dietary supplements lack specific growth promoting or immune stimulating effects in juvenile channel catfish. We also fed fry of Nile tilapia a basal diet supplemented with commercially available probiotic microorganisms. Survival, growth, disease resistance, and immunological parameters were monitored for a maximum of 94 days. Bacterial populations were higher in the digestive tracts of tilapia receiving probiotic diets, and colony morphology suggested that viable probiotic bacteria persisted up to 48 hours after feeding. Survival was higher after 39-63 days in fish receiving Bacillus spp. There was no difference in growth, lysozyme, total serum immunoglobulin, complement, specific anti-streptococcal antibody levels, or mortality due to Streptococcus iniae infection after disease challenge. The results suggest that these commercially available probiotic microorganisms do not provide beneficial effects in young Nile tilapia. Experiments are currently in progress to evaluate beta-glucan prebiotic diet supplements which are reported to stimulate immune function in fish. These polysaccharide cell wall components of yeasts enhance non-specific immunity and may be useful to control disease in aquaculture.