Doctor of Philosophy (PhD)


Animal Sciences

Document Type



Aquaculture plays a big part in boosting global fish production and it has become a valuable activity for developing countries playing an important role in their poverty reduction plans. The increasing demand for food fish production leads to the expansion and intensification of aquaculture practices which usually involve high stocking densities. This may have a negative effect on growth and allows the occurrence of infectious diseases, such as enteric septicemia of catfish caused by Edwardsiella ictaluri, leading to high mortalities. This work evaluated the addition of fructooligosaccharides, isomaltooligosaccharides, xylooligosaccharides, and galactooligosaccharides as dietary supplements and their effect on growth of goldfish, Nile tilapia, and channel catfish; and disease resistance and survival of channel catfish after challenge with Edwardsiella ictaluri. Results in this study indicated no statistically significant differences in growth and condition factor of goldfish and tilapia fed the different diets. Alpha and Beta diversity indexes results showed that goldfish and tilapia fed the different diets had similar intestinal microbial composition. Fish fed diet Six showed the highest microbial diversity among the goldfish group. Fish fed diet Five showed the highest microbial diversity among the tilapia group. In the channel catfish group, statistically significant differences were found between stocking densities and individual weight of fish fed the different diets, but differences in condition factor were not statistically significant. Significant differences were found in survival of fish challenged with E. ictaluri with diet Two (63.3%) showing the highest survival rate and diet Five (20%) showing the lowest survival rate. Diet Four showed the highest gut microbial diversity when compared to the rest of the diets. Similarity and dissimilarity indexes showed that the microbial population of channel catfish fed the different diets was very diverse, although evenly distributed since in most of the cases Edwardsiella was the predominant genus. Results in this study suggest that the use of commercial prebiotics in aquaculture may potentially shape gut microbiome and improve fish survival. Further research is still needed; the use of different prebiotic concentrations, possible prebiotics combinations, and changes in the duration of the feeding trials might yield different results.



Committee Chair

Elzer, Philip

Available for download on Wednesday, July 03, 2030