Abstract #460

# 460
The genomic architecture of inbreeding: How homozygosity affects health and performance in dairy cattle.
Christine F. Baes*1, Filippo Miglior1,2, Bayode Makanjuola1, Calista Vogelzang1, Flavio Schenkel1, Jeremy T. Howard3, Christian Maltecca4, Gabriele Marras1, 1Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, Canada, 2Canadian Dairy Network, Guelph, ON, Canada, 3Department of Animal Science, University of Nebraska, Lincoln, NE, 4Department of Animal Science, North Carolina State University, Raleigh, NC.

Inbreeding depression is a growing concern in livestock production because it detrimentally affects fitness, health and welfare of animals. Genomic information can be analyzed to better capture Mendelian sampling, thereby enabling more accurate estimation of inbreeding. Continuous stretches of homozygous genotypes (runs of homozygosity, ROH) have been shown to provide a better estimate of autozygosity at the genomic level than conventional measures based on pedigree information alone. The objective of this study was to identify ROH associated with traits of economic importance in the Canadian Holstein population. Genotypes and phenotypic records were extracted from the Canadian Dairy Network database for all Holstein cows that had their first calving after January 1st, 2000. The different traits analyzed included milk production traits and various other traits of economic importance. Haplotypes contained within a ROH were identified and associated with the relevant traits using a 3-step algorithm. Genomic information and identification of ROH allow for the examination of the impact of homozygosity on recorded phenotypes on a genome-wide level, but also at specific regions of the genome. Multiple haplotypes when contained within a ROH were identified that had a consistent unfavorable effect both within and across groups of traits. Further investigation of these haplotypes and better understanding of their effects will be useful for a better understanding of the detrimental effects of homozygosity on fitness, health, and welfare of dairy cattle.

Key Words: genomic inbreeding, runs of homozygosity, autozygosity

Speaker Bio
Christine Baes took up the Semex–Canadian Dairy Network (CDN) – Holstein Canada Professorship in Dairy Genomics at the University of Guelph in Canada in 2015. Her research interests include analysis of genomic inbreeding, development of new methodologies to exploit next generation genomics data, novel phenotypes, and studies involving the economic value of traits implemented in breeding programs.