EVALUATION OF A STRESS RESPONSE FOR USE IN A SELECTIVE BREEDING PROGRAM FOR IMPROVED GROWTH AND DISEASE RESISTANCE IN RAINBOW ROUT (ONCORHYNCHUS MYKISS)

Authors: Weber, Gregory - Greg; Silverstein, Jeffrey

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2006
Publication Date: 12/14/2006
Citation: Weber, G.M., Silverstein, J. 2006. Evaluation of a stress response for use in a selective breeding program for improved growth and disease resistance in rainbow rout (oncorhynchus mykiss). North American Journal of Aquaculture. 69:69-79.

Interpretive Summary: A breeding program to develop improved animals for the US rainbow trout aquaculture industry is being conducted at the USDA ARS National Center for Cool and Cold Water Aquaculture. Stress has been shown to have negative impacts on many traits important to the aquaculture of rainbow trout including growth rate, feed efficiency, disease resistance, and reproductive performance, all of which are performance traits under consideration for improvement in our broodstock. A stakeholders' meeting held at NCCCWA in July of 2001 identified mitigation of problems associated with stress as an important objective for research at NCCCWA. Consequently we have been characterizing broodstock families for a stress response, and evaluating if this stress response is associated with performance traits of interest to the US rainbow trout aquaculture industry. The stress response we are using is blood cortisol and glucose concentrations following a 3 hour confinement stress. Cortisol is the primary hormone regulating the body's response to stress and an increase in blood glucose is one of these responses. We found the method to identify differences in this stress response to be reliable. Size of the fish within the range examined and sex of the animals, which were reproductively immature, did not appear to affect response. Survival rate was 70% and there was no association between survival and post-stress blood cortisol or glucose concentrations. There was a significant positive association between post-stress blood cortisol levels and growth performance. In addition, we selected animals for breeding based on growth performance and found that the values for post-stress blood cortisol concentrations were significantly greater for families selected for faster growth rate, than for those not selected. Thus, we may be unintentionally altering stress response in our fish as part of our selection process for improved growth.

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 Cold Water Aquaculture. Although current selection efforts are based on growth and disease resistance, stress responsiveness is also a concern. Previous work has shown that heritable differences in stress response can be identified by measuring blood levels of cortisol following exposure to a three hour crowding stress. We characterized this stress response and measured plasma glucose concentrations in 64 of our broodstock families. We found the method to identify differences in this stress response to be reliable. Values for both cortisol and glucose response were similar for replicates of families. Size of the fish within the range examined and sex of the animals, which were reproductively immature, did not appear to affect response. Variation in post-stressor plasma cortisol and glucose was observed among strains, families, and individuals. Most of the variation in cortisol response due to strain was attributable to the maternal parent. The cortisol and glucose responses to the stressor were not correlated. Resting and post-stressor plasma cortisol concentrations but not glucose concentrations among families were significantly correlated. Survival rate was 70% and there was no association between survival and post-stressor cortisol or glucose concentrations. There was a significant positive association between cortisol response and growth performance, and mean plasma cortisol concentrations in response to the stress challenge was significantly greater for families selected for faster growth rate, than for those not selected.