Selecting sires to improve reproductive success: key traits for enhanced fertility and embryo development.

Embryo development is a complex process that requires several physiological and molecular events to happen harmoniously, and all of this begins with the interaction of the oocyte and sperm. The ability of an oocyte to become a healthy blastocyst is the result of several critical events that are determinants for the successful development of the embryo. Among these events are the sperm's ability to interact with and penetrate the oocyte, carry out syngamy, the developmental competence of the oocyte to support mitotic divisions, and the proper activation of the molecular machinery to regulate the embryo's developmental competence during the early stages of embryonic development. Some of these events originate from either the paternal or maternal side. The focus of this review is to explore the contributions of the paternal side to reproduction in general, with greater emphasis on early embryo development. A deeper understanding of these paternal factors and their influence on embryo development and overall fertility will support the development of new strategies for selecting sires to improve reproductive efficiency in cattle.