Bioeconomics of Flavobacterium columnare vaccine pond trials for channel catfish Ictalurus punctatus
Type of DegreeMaster's Thesis
Fisheries and Allied Aquacultures
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The US farm-raised catfish industry has had a variety of problems in the last decade, both in production and marketing. Increased disease pressures have come primarily from the ubiquitous pathogens responsible for columnaris (COL, Flavobacterium columnare), enteric septicemia of catfish (ESC, Edwardsiella ictaluri), and virulent Aeromonas hydrophila (vAh). Pond trials were conducted with vaccinated fish using an experimental live-attenuated COL vaccine, and non-vaccinated channel catfish (Ictalurus punctatus). Data were collected to evaluate the COL vaccine for survival, growth, feed conversion, antibody presence, and economic benefit. These trials were a follow-up to promising laboratory results, which confirmed that the 17-23 vaccine increased protection against F. columnare in channel catfish fry. Pond trials represent an environment more akin to commercial catfish operations which use earthen ponds. Channel catfish fingerlings were split into either a control or vaccinated treatment, with five ponds per treatment (n=5). Control fish were stocked at a rate of 741 fish per pond, while treatment fish were vaccinated through bath immersion before being stocked into their respective ponds (777 fish/pond). Fish were fed a 32% crude protein floating pellet from stocking in April 2019 until harvest in October 2019. Routine and periodic fish growth sampling and blood collection were performed throughout the trial. No COL disease challenge was conducted, although the production timeline overlapped with two known columnaris outbreak peaks which occur in the spring and fall as seasonal water temperatures change. Experimental units included ten 0.04-hectare watershed ponds, each with one 0.5 hp aerator running from 6pm to 8am daily. Blood serum samples were processed and analyzed for antibody concentrations with an indirect ELISA (enzyme-linked immunosorbent assay). Results showed no significant increase in survival of vaccinated fish compared to control fish (P = 0.7127), and there were no natural outbreaks of COL observed during the trials. Results of an indirect ELISA determined that the anti-COL antibody concentrations were significantly higher in vaccinated fish 4 weeks post-stocking (P < 0.05), but not at 8 weeks post stocking (P=0.334). Vaccinated fish (357.5 ± 30g) had a significantly higher average weight at harvest than control fish (289.3 ± 20g) (P =0.0013), and the FCR of vaccinated fish (1.35) was lower than control fish (2.13), representing a 37% FCR improvement (P < 0.0001). The total amount of feed fed decreased from the control to vaccinated treatment by 14% but was not significant due to high variability among vaccinated ponds (P = 0.1195). Without a large mortality event we were not able to assess the vaccine’s impact on survival, but the vaccine impacts to production parameters (feeding amounts, FCR, biomass harvested) are encouraging. Our partial budgets present the minimum economic benefit to a producer on the research level, as well as potential net benefits on a more applicable commercial scale. Feed efficiency appears to be the catalyst for the benefits observed in this trial in which there was no observable or measurable incidence of columnaris. While the data is encouraging for commercial farmers, further production studies are warranted in which measured disease incidences are recorded to further corroborate the benefits of disease management through this columnaris 17-23 vaccine adoption.