|MA, LI - University Of Maryland|
|DA, YANG - University Of Minnesota|
Submitted to: Journal of Dairy Science
Publication Type: Review Article
Publication Acceptance Date: 8/16/2018
Publication Date: 4/1/2019
Citation: Ma, L., Cole, J.B., Da, Y., Van Raden, P.M. 2019. Symposium review: Genetics, genome-wide association study, and genetic improvement of dairy fertility traits. Journal of Dairy Science. 102(4):3735-3743. https://doi.org/10.3168/jds.2018-15269.
Interpretive Summary: Low fertility is a current challenge to the dairy industry. Genetic selection of fertility related traits started since 2002 in the US. With the implementation of genomic selection in 2009, promising changes have been observed for dairy fertility. Meanwhile, genetic and genome-wide association studies of dairy fertility investigated the genetic basis of fertility traits. This review aims to provide an overview of female dairy fertility traits, the genetic contribution to fertility, related genomic regions and genes, and recent genetic improvement of dairy fertility in the US.
Technical Abstract: Before fertility traits were incorporated into selection, dairy cattle breeding primarily focused on production traits, which resulted in an unfavorable decline in the reproductive performance of dairy cattle. This reduced fertility is constantly challenging the dairy industry on the efficiency and sustainability of dairy production. Recent development of genomic selection on fertility traits has stabilized and even reversed the decreasing trend, showing the effectiveness of genomic selection. Meanwhile, genome-wide association studies have been performed to identify QTL and candidate genes associated with dairy fertility, providing a better understanding of the genetic architecture of fertility traits. In this review, we seek to provide an overview of the genetics of fertility traits, to summarize the findings from existing GWAS of female fertility in dairy cattle, and to update the recent research progress in US dairy cattle. Because of the polygenic nature of fertility traits, many GWAS of dairy fertility tended to be underpowered. Only one major QTL, on BTA18, was identified across multiple studies. This QTL was associated with a range of fertility traits from conception to calving, but the candidate gene/mutation is still missing. Collectively, with the promising success from genomic selection but low power of GWAS on dairy fertility traits, this review calls for continuous data collection of fertility traits to enable more powerful studies of dairy fertility in the future.