Location: Cool and Cold Water Aquaculture Research
Title: Cortisol response to a crowding stress: Heritability and association with disease resistance to Yersinia ruckeri in rainbow trout Authors
Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: August 30, 2006
Publication Date: February 26, 2007
Citation: Weber, G.M., Lankford, S., Silverstein, J., Vallejo, R.L., Welch, T.J. 2007. Cortisol response to a crowding stress: Heritability and association with disease resistance to Yersinia ruckeri in rainbow trout. Book of Abstracts Aquaculture America. Technical Abstract: A breeding program to develop improved germplasm for the US rainbow trout aquaculture industry is being conducted at the USDA ARS National Center for Cool and Coldwater Aquaculture. Current selection efforts are based on growth and disease resistance, but stress response is also a concern. Using plasma cortisol concentrations following a three hour crowding stress challenge (8 fish per family, stressed 4 times) as our measure for stress responsiveness, we have previously shown that significant family variation in cortisol responsiveness exists within our broodstock, and cortisol responsiveness is positively correlated with growth performance. Since we are selecting based on growth performance we can expect cortisol responsiveness to increase in subsequent generations if cortisol responsiveness is heritable. The objectives of the present phase of this project were to calculate heritability of cortisol responsiveness, and determine if it is associated with disease resistance. Narrow-sense heritability for cortisol responsiveness was estimated using nested and full-sib family designs and Proc Mixed procedure with repeated measurement analysis (SAS 2003), h2 > 0.40. Separate individuals from the same families were used to determine cortisol responsiveness and resistance to Yersinia ruckeri, the pathogenic agent of enteric redmouth disease, in an immersion challenge. Breeding values for cortisol response were estimated using the Proc Mixed procedure (SAS 2003) and breeding values for Yersinia survivability were estimated using methods of survival analysis implemented in the SURVIVAL KIT version 3.12 program (Ducrocq and Sölkner, 1998). Breeding values for cortisol responsiveness and survivability were not correlated. This was true when the fish were not stressed before the disease challenge, and when they first experienced repeated daily exposure to a crowding stress. However, there was also no correlation of disease survival breeding values between the stressed and unstressed families, suggesting possible variation in the effect of stress on disease resistance among families. Breeding values for plasma lysozyme activity, glucose, and chloride levels also did not correlate with survivability in stressed and unstressed fish.