Symposium review: The genomic architecture of inbreeding: How homozygosity affects health and performance

摘要

Inbreeding depression is a growing concern in livestockbecause it can detrimentally affect animal fitness,health, and production levels. Genomic information canbe used to more effectively capture variance in Mendeliansampling, thereby enabling more accurate estimationof inbreeding, but further progress is still required.The calculation of inbreeding for herd managementpurposes is largely still done using pedigree informationonly, although inbreeding coefficients calculated inthis manner have been shown to be less accurate thangenomic inbreeding measures. Continuous stretches ofhomozygous genotypes, so called runs of homozygosity,have been shown to provide a better estimate of autozygosityat the genomic level than conventional measuresbased on inbreeding coefficients calculated throughconventional pedigree information or even genomicrelationship matrices. For improved and targeted managementof genomic inbreeding at the population level,the development of methods that incorporate genomicinformation in mate selection programs may provide amore precise tool for reducing the detrimental effects ofinbreeding in dairy herds. Additionally, a better understandingof the genomic architecture of inbreeding andincorporating that knowledge into breeding programscould significantly refine current practices. Opportunitiesto maintain high levels of genetic progress in traitsof interest while managing homozygosity and sustainingacceptable levels of heterozygosity in highly selecteddairy populations exist and should be examined moreclosely for continued sustainability of both the dairycattle population as well as the dairy industry. Theinclusion of precise genomic measures of inbreeding,such as runs of homozygosity, inbreeding, and matingprograms, may provide a path forward. In this symposiumreview article, we describe traditional measures ofinbreeding and the recent developments made towardmore precise measures of homozygosity using genomicinformation. The effects of homozygosity resulting frominbreeding on phenotypes, the identification and mappingof detrimental homozygosity haplotypes, managementof inbreeding with genomic data, and areas inneed of further research are discussed.