Sexed Semen in the Beef Industry
When you have good herd genetics, there have probably been times you wished you could control the sex of the calves. You’ve probably had the thought: “I wish more of these were heifers” (or bulls, depending on your goals). For decades, the sex of a calf crop was essentially a coin flip, and you get what you get. Now, thanks to some pretty incredible leaps in technology, that “luck of the draw” is becoming a thing of the past. Now you can have that cow with good genetics have heifers. Or, you can have more bulls, depending on your farm or ranch and the goals you’re trying to accomplish.
Semen sexing has come a long way in the cattle industry, evolving from an experimental idea into a practical breeding tool used on farms every year. Technology allows producers to almost guarantee whether a cow has a bull or a heifer calf. The dairy industry has led the way, using sexed semen to boost heifer numbers and speed genetic progress, while beef producers are beginning to adopt it more strategically as the technology improves. Semen sexing has moved from a high-tech novelty to a practical tool for beef producers. Just like any tool, it works best when you understand how it’s built and exactly when to pull it out of the shed.
What Exactly Is Semen Sexing?
At its core, sexing semen is a literal cell-by-cell sorting process. The industry standard is flow-cytometric sorting. Flow-cytometric sorting is the process used to separate sperm based on whether they carry an X or Y chromosome. Each sperm cell is stained with a DNA-binding dye and passed single-file through a laser, which measures a tiny difference in DNA content between X- and Y-bearing sperm. The cells are then electrically sorted into separate groups, allowing producers to use semen that is heavily biased toward producing either male or female calves.
Imagine a stream of sperm cells being focused into tiny, single-cell droplets. Each droplet passes by a laser that measures its fluorescence. Because X-chromosome sperm contain slightly more DNA than Y-chromosome sperm, they glow differently. The machine detects that signal in real-time, gives the droplet an electrical charge, and “deflects” it into the appropriate “X” or “Y” collection tube.
It is an incredibly precise process, but it’s also a high-pressure environment for the sperm. Because the process involves staining, lasers, and physical sorting, the resulting “sorted” sperm can be a bit more fragile than their unprocessed counterparts. This is where we see less viable sperm. This is where some advancements have really helped fertility rates.
SexedULTRA semen is an improved form of sex-sorted bovine semen developed by STgenetics to address the fertility losses seen with earlier sexed semen products. It was introduced commercially around 2013. Between using more advanced methods in sorting and extenders, we have seen an improvement in sperm viability while maintaining high sex-sorting accuracy. Later advancements, including SexedULTRA 4M, further increased sperm numbers per straw and helped narrow the conception rate gap between sexed and conventional semen, making the technology more practical for widespread on-farm use. This helped increase pregnancy rates in cattle.
Purity vs. Reality
When you buy a straw of sexed semen, you’re usually looking at a purity of about 85–95% (with 90% being the industry sweet spot). This means out of 100 sperm in the straw, 90 of them carry the chromosome you want. They’re sorted by the process described above. Even though it is an advanced system, the companies selling sexed semen do not guarantee 100%.
Knowing the purity, it is important to make a distinction that purity is not the same as pregnancy outcome. Purity is how clean the sample is in the lab. Whereas, sex outcome is the actual percentage of calves born of the desired sex. So, if you are buying semen with a purity of 85% female, that does not guarantee 85% of your inseminated cows are going to have heifers. While these numbers usually track somewhat close together, biology happens. Even with 90% purity, you’ll occasionally get an “exception”. Because sorted straws typically contain a lower sperm dose than conventional straws, the industry had to develop better extenders and hardware, like the SexedULTRA 4M technology, to make these lower doses more effective in the field.
The “Fertility Gap”
Let’s talk about conception rates. Historically, sexed semen had a reputation for poor performance, sometimes showing a 20–25% drop in pregnancy rates compared to conventional semen. However, with more advancements and refining, that gap is shrinking. Modern products like SexedULTRA have narrowed that penalty to roughly 10–18% in many trials. If you’re working with high-fertility heifers under optimal conditions, that gap can shrink even further to the 10-15% range.
There are a couple of studies that show us what to expect when using sexed semen. The first one is Reese et al., 2021 “The reproductive success of bovine sperm after sex-sorting”. In this study, they analyzed 45 studies and 72 trials. There was a lot of data and they were able to conclude that the overall use of sex-sorted sperm was associated with reduced non-return and pregnancy rates versus conventional semen.
Prior to this study, there were earlier studies showing large reductions. However, when they analyzed more recent data (including SexedULTRA era), the magnitude of the reduction was smaller but still significant. When restricted to post-2015 SexedULTRA frozen semen in heifers, the observed reduction was smaller (~~13–18% lower pregnancy rate vs conventional in pooled estimates).
This study tells us that there is a pregnancy gap between using sexed semen versus a bull or conventional ways. With sexed semen you will have lower pregnancy rates, so you will have to get a plan to pregnancy check and then impregnate the open heifers or cows. It also shows that sticking to post-2015 “ultra” products which use gentler processing and higher sperm concentrations (4M) per straw. However, the BIG advantage is you can profit off choosing the sex of the calf. You need to think about your current operation, your goals to figure out if it is a good fit for your operation.
The next trial we are going to look at is Kasimanickam et al., which was a commercial-operation trial comparing SexedULTRA inseminations to conventional semen. They tried to mimic real-world beef herd conditions to give us a good idea of what to expect.
With this study, they found that SexedULTRA gave a markedly higher proportion of female offspring (>90% female calves in the X-sorted group), but pregnancy outcomes varied by condition and often remained somewhat lower than conventional. The research is useful as a real-world example of sex ratio success plus the practical fertility tradeoffs.
So, how do you close the gap on your ranch? The studies find that using sexed semen on your most fertile animals, specifically heifers and first-service cows yields the best results.
When it comes to timing, there is a trial that sheds some light on best practices for timing the AI of sexed semen. Moore et al., 2023. On this study, they analyzed trials on heifers showing effects of delayed AI timing relative to estrus when using sexed semen.
From this study, we learned a lot about timing. Delaying insemination by about 8 hours (compared to standard timing) improved pregnancy per AI. In one example on their trail, pregnancy rates were increased 9% when delayed about 8 hours. This shows management (timing) can materially reduce the pregnancy gap.
Is Semen Sexing a Good Fit for my Cattle?
Semen sexing has become a reliable tool in the cattle industry today. Advances in technologies, particularly the introduction of products like SexedULTRA, have significantly improved semen quality and fertility compared with earlier generations of sex-sorted semen. While conception rates with sexed semen can still be lower than those achieved with un-sorted, conventional semen, cow and heifer selection, along with proper timing can greatly reduce this gap. Today, semen sexing is no longer experimental but a proven technology that continues to change. It’s a practical way to improve your herd efficiency, and when used according to your farm or ranch goals, it can help increase profits.
February 2026
By Jessica Graham
Here is another article from last month’s issue check it out!
