SELECTIVE BREEDING FOR ENHANCED SPECIFIC DISEASE RESISTANCE: PRATICAL CONSIDERATIONS AND POTENTIAL APPLICATIONS

Endemic infectious diseases constitute a considerable economic burden in aquaculture due to direct losses as well as indirect impacts on growth, animal welfare and transportation restriction. Host genetic variation in susceptibility to specific pathogens is present in most animal populations, especially aquatic animals due to outbred origin and short domestication history.  Recent progress in high-throughput animal health phenotyping combined with quantitative genetic analysis has demonstrated the feasibility of improving disease resistance through family-based selective breeding, and more recently, through genomic selection.  However, there are only a few examples of successful application of this control strategy in aquaculture and most stocks remain unselected. Salmonid fish are uniquely suitable for selective breeding as reproduction can be controlled, pedigrees can be tracked, large numbers of offspring are generated from each family, and embryo development can be temperature manipulated to synchronize hatching, thus disease resistance phenotyping can be performed using animals with similar body weight.  Herein, we review progress and associated logistics of our efforts toward breeding for specific disease resistance, using as an example, results generated from the National Center for Cool and Cold Water Aquaculture selective breeding program.  In addition, we discuss benefits and limitations of selective breeding and how it needs to be embedded within an integrated approach for controlling disease on-farm.