From sperm to pregnancy: insights into paternal regulation of fertility divergence in cattle.

Embryo development and pregnancy establishment require successful interaction between the oocyte and sperm and proper activation of developmental signaling pathways. In the bovine, the successful execution of this biological equation requires, on one hand, maternal determinants such as the intrinsic quality of the oocyte and molecules secreted by the endometrium epithelium critical to sustain embryo development. In contrast, paternal contributions encompass both visible sperm characteristics assessed by routine semen evaluation and hidden traits that escape conventional laboratory assessment of sperm quality. Paternal contributors extend beyond DNA delivery, as sperm also transfer a diverse array of molecules critical for reproduction. For instance, sperm can deliver proteins that could have short- and long-term consequences for sperm functionality, organelles that can be used to assemble the cytoskeleton machinery of the developing embryo, and other molecules that can regulate critical processes in reproduction to ensure the survival of different mammalian species. Taken together, paternal contributors can significantly influence fertility, with their impact manifesting at events occurring around fertilization with or without subsequent effects on embryo development and with or without consequences for pregnancy establishment, leading to the divergence in fertility observed among males.