A thorough understanding of the genetic factors that influence the feed efficiency of dairy cows is a prerequisite for planning and implementing selective breeding programs. Therefore, a systematic review of reported heritability, genetic markers, and biological pathways affecting FE-related traits in Holstein dairy cows was conducted and followed by a meta-analysis. A total of 47 articles were refined after literature screening and were presented in this review. A meta-analysis based on a random-effects model was then performed to combine the heritability estimates from studies. The meta-analysis showed heritability estimates of residual feed intake, dry matter intake, and energy balance were 0.22, 0.34, and 0.24, respectively. The systematic review demonstrated that 169 significant candidate genes, 13 genetic markers, and 29 biological mechanisms were previously reported on FE in Holstein dairy cows. Involved candidate genes and biological mechanisms are presented mainly in four biological mechanisms (insulin-like growth factors axis, lipid metabolism, oxidative phosphorylation pathways, tryptophan metabolism). The meta-analysis of the reported candidate genes showed three statistically significant KEGG terms and four GO:BP terms, which mainly focused on ATP synthesis, electron transport chain, and OXPHOS pathway.

Read the full article in the Journal of Animal Science.