Variance and covariance estimates for resistance to bacterial cold water disease and columnaris disease in two rainbow trout breeding populations

Authors: SILVA, RAFAEL - Oak Ridge Institute For Science And Education (ORISE); Evenhuis, Jason; Vallejo, Roger; TSURUTA, SHOGO - University Of Georgia; Wiens, Gregory - Greg; MARTIN, KYLE - Troutlodge, Inc; PARSONS, JAMES - Troutlodge, Inc; Palti, Yniv; LOURENCO, DANIELA - University Of Georgia; Leeds, Timothy - Tim

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2018
Publication Date: 12/20/2018
Citation: Silva, R., Evenhuis, J., Vallejo, R.L., Tsuruta, S., Wiens, G.D., Martin, K., Parsons, J., Palti, Y., Lourenco, D., Leeds, T.D. 2018. Variance and covariance estimates for resistance to bacterial cold water disease and columnaris disease in two rainbow trout breeding populations. Journal of Animal Science. 97(3):1124-1132. https://doi.org/10.1093/jas/sky478.
DOI: https://doi.org/10.1093/jas/sky478

Interpretive Summary: Family-based selective breeding is an effective strategy for controlling diseases in aquaculture. In this study we analyzed infection response data from up to five generations and estimated variance components for resistance to Bacterial Cold Water Disease and Columnaris Disease in two rainbow trout nucleus breeding populations important for US aquaculture. We found moderate heritabilities for the two disease resistance traits in both populations and also moderate and significant positive genetic correlation between the two traits. The study results indicate that progress can be achieved through selective breeding for resistance to bacterial pathogens in rainbow trout aquaculture, and that selection for improved resistance to one pathogen will also improve the population resistance to the other pathogen. Collectively, these data support the role of selective breeding in reducing mortalities and antibiotic use in rainbow trout aquaculture when fish are exposed to these pathogens.

Technical Abstract: Family-based selective breeding is an effective strategy for controlling diseases in aquaculture. This study aimed to estimate (co)variance components for resistance to Bacterial Cold Water Disease (BCWD) and Columnaris Disease (CD) in two rainbow trout nucleus breeding populations: the USDA-ARS National Center for Cool and Cold Water Aquaculture odd-year line (ARS-Fp-R) and the Troutlodge, Inc., May-spawning odd-year line (TLUM), which provided 46,805 and 27,821 pedigree records, respectively. Between 44 and 138 families per generation and population were evaluated under controlled BCWD and CD challenges, providing 32,311 and 17,861 phenotypic records for BCWD resistance, and 13,603 and 9,413 for CD resistance in the ARS-Fp-R and TLUM populations, respectively. A two-trait animal threshold model assuming an underlying normal distribution for the binary survival phenotypes was used estimate the (co)variance components separately for each population. The results indicate that the traits of resistance to BCWD and CD are heritable (BCWD - h2=0.27±0.04 and 0.43±0.08; CD – h2=0.23±0.07 and 0.34±0.09, for the ARS-Fp-R and TLUM populations, respectively). The genetic correlation between the resistance to BCWD and CD was favorably positive in both studied populations (0.40±0.17 and 0.39±0.18, respectively for ARS-Fp-R and TLUM). These findings suggest that both traits can be improved simultaneously even if genetic selection pressure is applied to only one of the two traits.