Grant: Alliance Grants

To allow breeding strategies that improve cattle genetic management, a billion-dollar industry exists to collect genetically optimal semen, freeze (cryopreserve) the sample, and ship the samples to farms around the world. Post-cryopreservation fertility recovery remains suboptimal and every percent of increased post-thaw fertility corresponds to millions of dollars in revenue, as samples from genetically valuable bulls can be divided into more portions. In the last decade, the use of (sexed) semen that has been processed to preferentially produce male or female offspring has grown dramatically. The loss in post-thaw fertility is especially felt in sexed semen, where post-thaw recovery is reduced by a third over conventional semen. In fact, because the semen sexing process is expensive and time consuming, it would be valuable to industry to have a pre-freeze test that allows for the prediction of potential post-thaw fertility. Semen are cryopreserved in a media that contains chemical additives to protect from a range of possible damages that occur during cryopreservation. Most studies aiming to improve semen cryopreservation adjust the concentrations of media components one or two at a time, but considerable interaction among media components, semen quality, and post-thaw recovery reduces the power to identify a standard recipe for large scale industrial processes. We recently used a novel large-scale machine learning informed experimental design to optimize an 11 component media recipe for cryopreservation of conventional (non-sexed) semen, resulting in a recipe exceeding industry standard post-thaw motility. Based on this success, we propose to apply what we have learned from our conventional semen experimental design to continue to improve the post-thaw fertility in non-sexed semen, and to improve the post-thaw fertility in sexed dairy and beef semen. Second, based on our preliminary data, we propose three novel tests of semen quality that we believe will provide predictions of post-thaw fertility. This research will improve comparative cryopreservation of sexed and nonsexed semen, improved post-thaw fertility for all semen, and predictive tests of the post-thaw fertility.