The 'omics' revolution: Use of genomic, transcriptomic, proteomic and metabolomic tools to predict male reproductive traits that impact fertility in livestock and poultry.

Fertility is an important economic trait in livestock and poultry that relies on the genetic merit of both males and females. Despite the importance of the paternal contribution to reproductive success, the preponderance of research has focused on the female. The advent of the 'omics' era has stimulated the search for accurate predictors of male fertility, which is especially important for animal production where the fertility status of males most often is not known until sexual maturity is reached, and methods to assess semen quality often are not correlated with fertility, especially subfertile males. Identification and validation of biomarkers, such as genes, transcripts, proteins, metabolites, that are associated with fertility phenotypes has great potential to improve the reproductive efficiency of livestock and poultry. Recent findings of candidate genes and biomarkers primarily associated with semen and sperm are highlighted for the major agricultural species.