Mapping Cytokine Genes in Food Animals
The breeding of domesticated animals used for food production has been directed primarily at increasing performance as measured by milk production, growth rate, reproductive success, and carcass quality. Only recently is emphasis being placed on the selection of animals based on disease resistance even though a variety of diseases are known to have a genetic component (1). Rather, intensive livestock production systems have employed extensive and expensive antibiotic and chemoprophylactic methods to maintain herd health. Moreover, vaccines for several important veterinary pathogens are either not available or not economically feasible, and there is a growing public interest for producing “natural” food supplies. Thus, it becomes necessary to identify genes that influence both general and disease-specific immunocompetence. Once correlations between cytokine genotypes and disease resistance are identified, these markers can be incorporated into breeding selection criteria. In this chapter, we will discuss: (a) the correlation between cytokine expression and the resistance or susceptibility to specific diseases; (b) techniques used to genetically map the 422chromosomal location of specific genes; and (c) the status of the genetic mapping of cytokine and cytokine receptor genes for economically important animal species.