Response to selection for bacterial cold water disease resistance in rainbow trout

Authors: Leeds, Timothy - Tim; Silverstein, Jeffrey; Vallejo, Roger; Palti, Yniv; Rexroad, Caird; Evenhuis, Jason; Hadidi, Sima; Weber, Gregory - Greg; Welch, Timothy - Tim; Wiens, Gregory - Greg

Submitted to: International Symposium on Genetics in Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: 6/22/2009
Publication Date: 6/22/2009
Citation: Leeds, T.D., Silverstein, J., Vallejo, R.L., Palti, Y., Rexroad III, C.E., Evenhuis, J., Hadidi, S., Weber, G.M., Welch, T.J., Wiens, G.D. 2009. Response to selection for bacterial cold water disease resistance in rainbow trout. International Symposium on Genetics in Aquaculture.

Interpretive Summary:

Technical Abstract: Previous studies indicate that resistance to experimental bacterial cold water disease (BCWD) challenge is heritable and thus may be improved through selective breeding. Our objective was to estimate response after one generation of genetic selection for resistance to BCWD in a pedigreed population of rainbow trout (Oncorhynchus mykiss). Fish (n = 4,735) sampled from 75 full-sib families hatched in 2005 (base generation) were injected i.p. with 6.5 × 10^6 CFU of Flavobacterium psychrophilum (CSF259-93) at a body weight of 2.3 +/- 0.35 grams, and survival was monitored for 21 days. Heritability of post-challenge survival and family breeding values were estimated from an animal model, and selection and mating decisions were made using optimum genetic contribution theory to maximize genetic gain and constrain inbreeding to < 1% per generation. Twelve families were selected and mated to produce 63 full-sib families, and three mixed-family control strains were propagated using random mating. Progeny of selected families and control strains were hatched in 2007 (first generation), and 4,276 fish were subjected to a similar challenge protocol to estimate phenotypic response. Heritability of post-challenge survival was moderate (0.26), and our selection differential was +29 percentage points in the base generation. Mean survival of select-line families increased from 29% (base generation) to 75% (first generation). After adjusting for relative survival of randomly-mated control strains (i.e., year effect), the observed phenotypic response to selection was +32 percentage points. Selection for BCWD resistance had no correlated effect on 10- and 13-month body weights or thermal growth coefficient. This study demonstrates that selective breeding can be effective for improving resistance to experimental BCWD challenge in rainbow trout, and selection response can be predicted with reasonable accuracy. Future studies comparing survival of select and non-select families following natural BCWD outbreak in a production setting are needed to validate our results.