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2009-Silverstein_et_al - Rainbow trout resistance to...

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Wiens and V. Ducrocq J. T. Silverstein, R. L. Vallejo, Y. Palti, T. D. Leeds, C. E. Rexroad III, T. J. Welch, G. D. not adversely correlated with growth Rainbow trout resistance to bacterial cold-water disease is moderately heritable and is doi: 10.2527/jas.2008-1157 originally published online November 21, 2008 2009, 87:860-867. J ANIM SCI http://jas.fass.org/content/87/3/860 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by guest on October 11, 2011 jas.fass.org Downloaded from
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ABSTRACT : The objectives of this study were to estimate the heritabilities for and genetic correlations among resistance to bacterial cold-water disease and growth traits in a population of rainbow trout ( Onco- rhynchus mykiss ). Bacterial cold-water disease, a chron- ic 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 used in aquaculture. At the same time, improving growth performance is 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 g, 71 full-sib families were challenged with F. psychrophi- lum and evaluated for 21 d. Overall survival was 29.3% and family rates of survival varied from 1.5 to 72.5%. Heritability of postchallenge survival, an indicator of disease resistance, was estimated to be 0.35 ± 0.09. Body weights at 9 and 12 mo posthatch and growth rate from 9 to 12 mo were evaluated on siblings of the fish in the disease challenge study. Growth traits were moderately heritable, from 0.32 for growth rate to 0.61 for 12-mo BW. Genetic and phenotypic correla- tions between growth traits and resistance to bacterial cold-water disease were not different from zero. These results suggest that genetic improvement can be made simultaneously for growth and bacterial cold-water disease resistance in rainbow trout by using selective breeding. Key words: challenge test, disease resistance, genetic correlation, growth, heritability, rainbow trout ©2009 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2009. 87:860–867 doi:10.2527/jas.2008-1157 INTRODUCTION Bacterial cold-water disease ( BCWD ), a chronic dis- ease of rainbow trout ( Oncorhynchus mykiss ), is com- mon in US rainbow trout aquaculture and is caused by Flavobacterium psychrophilum ( Fp ). This bacterium also causes acute losses in young fish, known as rainbow trout fry syndrome. Methods for prevention of BCWD are limited, and no licensed vaccine is currently avail- able. There is evidence of genetic variation for resistance to Fp infection in salmonids. For example, Nagai et al. (2004) showed differences in susceptibility to Fp challenges among 3 stocks of ayu ( Plecoglossus altive- lis ), and Henryon et al. (2005) showed significant ad- ditive genetic variation for resistance to Fp challenge in a Danish rainbow trout broodstock. This evidence
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