Location: Cool and Cold Water Aquaculture Research
Title: On-farm performance of rainbow trout (Oncorhynchus mykiss) selectively bred for resistance to bacterial cold water disease: effect of rearing environment on survival phenotype Authors
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2013
Publication Date: March 25, 2013
Repository URL: http://handle.nal.usda.gov/10113/56836
Citation: Wiens, G.D., Lapatra, S.E., Welch, T.J., Evenhuis, J., Rexroad III, C.E., Leeds, T.D. 2013. On-farm performance of rainbow trout (Oncorhynchus mykiss) selectively bred for resistance to bacterial cold water disease: effect of rearing environment on survival phenotype. Aquaculture. 388-391:128-136. Interpretive Summary: A frequent cause of fresh water farmed trout loss is bacterial cold water disease (BCWD). Since 2005, we have selectively bred a line of rainbow trout with higher resistance against BCWD. Two additional lines, a control and susceptible line, have been bred in order to better understand how we have changed rainbow trout disease resistance properties by breeding. We conducted a series of experiments over three consecutive years that tested the performance of these fish when reared under farm conditions and exposed to natural BCWD infection. Our results indicated that our breeding program increased resistance to BCWD; however, the farm environment was also able to mask some of the differences between the selectively bred lines. While we do not completely understand this environmental influence, the overall higher survival of the resistant line following a BCWD outbreak supports the planning of large scale trials and the release of the resistant line to industry.
Technical Abstract: Selective fish breeding programs for disease resistance comprise an increasingly important role in aquaculture production and offer an additional management tool for reducing bacterial-caused disease losses. Bacterial cold water disease (BCWD) is one of the most frequent causes of elevated mortality in juvenile salmonids, and we have selectively bred three genetic lines of rainbow trout for varying resistance to BCWD. These lines, designated ARS-Fp-R (resistant), ARS-Fp-C (control) and ARS-Fp-S (susceptible), differ in survival following standardized laboratory challenges with the causative agent of BCWD, Flavobacterium pyschrophilum. This study evaluated survival of the genetic lines in laboratory challenges and in a production environment. Evaluations of disease resistance demonstrated a reproducible, 30% or greater, survival difference between ARS-Fp-R and ARS-Fp-S lines at body weights ranging from 0.7 to 13 g. Farm trials were performed to evaluate survival over an 80-day growth period starting after the trout began feeding. After a BCWD epizootic, the ARS-Fp-R line displayed significantly greater risk-adjusted survival (95.7%) than the ARS-Fp-S line (91.2%, P is less than 0.0001) and the ARS-Fp-C line (92.4%, P is less than 0.0001). Phenotype stability in farm-trial fish was also evaluated using laboratory challenges. The ARS-Fp-R line consistently displayed a higher, but not always statistically significant, survival percentage compared to the other lines and the data suggest that the magnitude of the survival phenotype difference is sensitive to environmental influence. In summary, the overall greater survival of the ARS-Fp-R line provides evidence of genetic improvement under production conditions.