Meta-assembly of genomic regions and variants associated with female reproductive efficiency in cattle

Decline in fertility in last few decades, especially in high milk producing dairy cows, is a major concern in many countries. Fertility is a compound trait of many events leading up to successful calving and subsequent lactation. Fertility traits in cattle have relatively low heritability. Recently a number of studies have searched for genomic regions and variants associated with various reproduction traits in cattle. We constructed a systematic meta-assembly of 35 QTL studies and separately for 23 genome-wide association studies (GWAS) related to female fertility in cattle representing over 101,000 genotyped individuals. We separately compiled and discussed additional candidate gene studies, fine-mapping studies, selection signatures and other novel potential biomarkers associated with female reproduction in cattle. Despite individual studies being low powered, inherent low heritability of fertility traits and low success of genomic selection for fertility traits, a substantial number of strong signals, causative mutations and biomarkers for fertility have been identified throughout the genome. A number of embryonic lethal mutations and haplotypes have been identified using novel approaches. These markers can be used for population screening, genomic-assisted mating plans, and can be incorporated in a marker assisted framework for genetic improvement in the fertility. The studies investigating the role of epigenomic markers are in the early stages, and may provide important biomarkers in near future. Novel approaches linking metabolomic and epigenetic markers, and high resolution genome content to high quality phenotypes will assist in our understanding of the genetic architecture of complex traits underlying fertility in cattle.