Selection under Challenging Environments
Max F. Rothschild · Iowa State University Digital Repository (Iowa State University) · 1991
Increased selection pressure applied to commercially important traits in production environments is often accompanied by increases in disease problems. At the same time selection for immune responsiveness and disease resistance has often been ignored by animal geneticists because of the difficulty of measuring these traits. Actual disease resistance to individual diseases would have to be measured under an environment that included disease challenge. Such testing could be prohibitively expensive. New opportunities to improve our understanding of the genetic nature of disease resistance now exist through the recent advances in molecular biology and immunology and make indirect selection for disease resistance possible. The major histocompatibility complex (MHC) genes exert a major role in control of disease resistance and all immune functions. Genetic considerations involved with testing and selection for disease resistance and improved immune responsiveness will require knowledge of the genetic correlations between disease resistance and immune responsiveness and production traits. Research suggests that antagonistic relationships between immune response, disease resistance and production traits might make simultaneous improvement of these traits difficult by conventional breeding and selection methods. Use of marker-assisted selection or gene-transfer methods with the genes of the MHC may offer an alternative approach for simultaneous improvement in all of these traits.