Gender-sorted semen has been used to successfully produce calves since 1992. Since then, the technology has evolved and become commercially available. Until recently, dairy producers mostly used gender-sorted semen, or semen used to select the gender of the calf. Now, it has found a place in the beef industry. At about 150 to 200% of the cost of conventional semen, it takes a certain management strategy to make it work.
Jordan Thomas, University of Missouri graduate student, is finding that pregnancy rates with timed AI does not work well with sex-sorted semen. "Part of it has to do with how long the sperm will retain fertility in the female reproductive tract," Thomas says. "Additionally, in a timed AI situation, you might only have half of the cows show heat by the time of AI."
Gonadotropin-releasing hormone, or GnRH, is used in timed AI protocols for this reason. "That product is used specifically because we're trying to get a tighter window of ovulation times and shorten what would have been a longer period of heat detection," Thomas says. "But when using sex-sorted semen, time breeding non-estrous females off GnRH administration is less effective."
Split-timed AI study
Thomas and the MU animal science department recently conducted a study looking at a split-timed method, using an Estrotect heat detection aid, a patch with gray-colored coating that scratches off when the cow is mounted by another to detect estrus. Using timed AI, cows that expressed estrus by the time of AI were inseminated then. The ones that didn't express estrus were inseminated 20 hours after the GnRH administration. "It was actually a pretty dramatic increase that we noted by doing that," Thomas says. "And it's an easy management strategy. Everything comes through that first day regardless of what their patch looks like. It's just a matter of sorting out those gray ones – that didn't express estrus."