IDENTIFICATION AND CHARACTERIZATION OF GENES AFFECTING COOL AND COLD WATER AQUACULTURE PRODUCTION
Location: Cool and Cold Water Aquaculture Research
Title: Rainbow trout resistance to bacterial cold-water disease is moderately heritable and is not adversely correlated with growth
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2008
Publication Date: November 21, 2008
Citation: Silverstein, J., Vallejo, R.L., Palti, Y., Welch, T.J., Wiens, G.D., Rexroad Iii, C.E., Ducrocq, V., Leeds, T.D. 2008. Rainbow trout resistance to bacterial cold-water disease is moderately heritable and is not adversely correlated with growth. Journal of Animal Science. 87:860-867.
Interpretive Summary: The gram-negative bacterium, Flavobacterium psychrophilum (Fp), which is the causative agent of bacterial cold-water disease (BCWD), poses a major fish health concern for trout and salmon aquaculture around the world, and has been documented to cause mortalities as high as 90% in some epizootics. Losses are especially severe in young fish, which may limit the use of vaccination as a control method. Methods for control of the disease are needed and selective breeding for disease resistant lines is a promising solution in the absence of approved, cost-effective vaccination methods. The objective of this study was to estimate the heritabilities for and genetic correlations among resistance to BCWD and growth traits in the base population of the selective breeding program for BCWD resistance rainbow trout at the National Center for cool and Cold Water Aquaculture (NCCCWA). Selective breeding for increased disease resistance is a promising strategy that has not been widely utilized in aquaculture. At the same time, improving growth performance is also critical for efficient production. The moderate to high heritability estimates for BCWD resistance and the lack of correlation between disease resistance and growth traits in this population suggest that significant gains can be made by selective breeding for rainbow trout disease resistance while maintaining top growth performance at the NCCCWA.
The objective of this study was to estimate the heritabilities for and genetic correlations among resistance to bacterial cold-water disease and growth traits in a population of rainbow trout. Bacterial cold-water disease, a chronic disease of rainbow trout, is caused by Flavobacterium psychrophilum. This bacterium also causes acute losses in young fish known as rainbow trout fry syndrome. Selective breeding for increased disease resistance is a promising strategy that has not been widely utilized in aquaculture. At the same time, improving growth performance is also critical for efficient production. At the National Center for Cool and Cold Water Aquaculture, reducing the negative impact of diseases on rainbow trout culture and improving growth performance are primary objectives. In 2005, when fish averaged 2.4 grams, 71 full-sib families were challenged with Flavobacterium psychrophilum and evaluated for 21 days. Overall survival was 29.3% and family rates of survival varied from 1.5 to 72.5%. Heritability of days to death, an indicator of resistance, was estimated to be 0.46 (+/- 0.09). The growth traits weight at 9 months, weight at 12 months and growth rate from 9 to 12 months were evaluated on siblings of the fish in the disease challenge study. Growth traits were moderately heritable, from h2 = 0.32 for growth rate to h2 = 0. 61 for 12 month body weight; the correlation between growth traits and resistance to bacterial cold-water disease was essentially zero.