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Sexed Semen

The current sexed semen product produced by Sexing Technologies and Cogent is marketed under the tradename Sexed ULTRA 4M. This product was evaluated in field trials conducted in Ireland in 2018 (AI after detected heat) and 2019 (fixed-time AI). In both trials, using bulls that were resident in a stud at the sex-sorting laboratory. The mean conception rate for sexed semen was poorer than conventional semen (2018: 50.2% vs. 60.3%; 2019: 50.1 vs. 61.1% for sexed and conventional, respectively). The conception rates achieved with sexed semen, on average, were 82% to 84% of those achieved with conventional semen.  Maximising conception rate with sexed semen requires careful animal selection, appropriate timing of AI, and attention to detail regarding straw handling. Read more on the research and get further advice on sexed semen in dairy herds here and at the links below.

Top results with sexed semen

Sexed semen can be successfully used to increase numbers of dairy female replacements born and to reduce the number of dairy bull calves born. Teagasc recommends that early calving younger cows or maiden heifers are most successfully bred to sexed semen. 

In addition sexed semen can be used to compact the birth of replacement heifers closer to the start of the calving season than when conventional semen is used. The challenge is the sperm is more fragile after the sorting process and sexed semen straws contain fewer sperm than conventional semen.

It is important to pay particular careful attention to straw handling and AI procedures. In the video below Jim White, Dairy Farmer outlines the reasons why he chose to use sexed semen. He has good fertility in his herd to begin with and as he has also sells surplus stock it gave him greater choice for his own herd and for growing his own herd. The video outlines the benefits and challenges of using sexed semen. 


Top results with sexed semen

How to improve likelihood of success with sexed semen

Sexed semen provides many potential advantages to dairy farmers. The most obvious and compelling reason to use sexed semen is because of the sex bias induced in the calf crop. Stephen Butler, Teagasc, Moorepark has some advice.

Why use sexed semen?

Sexed semen provides many potential advantages to dairy farmers. The most obvious and compelling reason to use sexed semen is because of the sex bias induced in the calf crop, with 90% of the pregnancies resulting in a heifer birth, and only 10% male dairy calves. This in turn means that more beef semen can be used, using bulls with high Dairy Beef Index. This will provide long term sustainability for the Irish Dairy Industry.

Some of the key factors that affect the likelihood of pregnancy establishment when using sexed semen have been identified. These are summarized in the text below and discussed in the following clip.

Using sexed semen

Guidelines for sexed semen usage 

Bull team

  • Pick highest EBI bulls available
  • Use a team of ≥5 bulls

Suitable dams


  • Target live-weight and BCS ≥3.25
  • Cycling regularly


  • Parity 1 to 4
  • >50 days in milk on day of AI
  • BCS ≥3.00
  • Cycling regularly
  • Free of postpartum disorders and uterine disease

When to use?

  • During the first 3 weeks of the breeding season, and within first 10 days if possible.

Timing of AI

  • 14 to 20 h after heat onset (first standing mount). Practice AM/PM rule if possible. If using once a day AI, use conventional semen if time of AI is <14 h after heat onset.

Fixed time AI

  • Costly, but mitigates risk
  • Facilitates targeted usage of sexed semen on mating start date

Straw handling on day of AI

  • Organise sexed straws into one goblet
  • Thaw 2 sexed semen straws at a time MAX
  • Thaw straws at 35 to 37 °C for 45 seconds
  • Load straws into pre-warmed AI guns, keep warm.
  • Deposit semen in uterine body
  • Complete inseminations within 5 mins

How many sexed semen straws do I need to use?

For farmers interested in using sexed semen, the first question often asked is how many straws do I need to use? First, identify the target number of replacement females that you want to have born on the farm. Second, decide if sexed semen will be used on heifers, on cows or on both. In the worked example below, a farmer with a 100 cow herd will use sexed semen on all the maiden heifers and on a targeted subset of high fertility lactating cows. Beef AI or beef stock bulls will be used on all repeats (heifers and cows) and any lactating cows not suitable for sexed semen. It is essential that all the guidelines in Box 1 above are implemented to maximise the chances of success with sexed semen. 

How many sexed semen straws do I need to use?