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.
Teagasc has outlined some of the key factors that affect the likelihood of pregnancy establishment when using sexed semen.
Guidelines for sexed semen usage
Use a team of bulls when using sexed semen; pick at least five bulls and select the highest EBI bulls available.
Both cows and heifers are suitable dams for sexed semen usage. When selecting heifers for sexed semen ensure that they are on target weight for their breed and body condition score (BCS) ≥3.25. These heifers should also be checked to ensure they are cycling regularly.
When selecting cows for sexed semen ensure that they are least 50 days in milk on day of artificial insemination (AI) and have a BCS ≥3.00.
These cows should be checked to ensure that they are cycling regularly and are free of postpartum disorders and uterine disease.
When to use?
The recommended time to use sexed semen is during the first three weeks of the breeding season, and within the first ten days if possible.
Timing of service should be between 14 to 20 hours after heat onset (first standing mount). Practice a.m/p.m rule if possible. If using once a day AI, use conventional semen if time of AI is <14 hours after heat onset.
Another point for farmers who want to use sexed semen to consider is synchronisation. It can be costly, but mitigates the risk of lower conception rates associated with sexed semen. Using synchronisation facilitates targeted usage of sexed semen on mating start date.
Straw handling
Teagasc recommends that you organise sexed straws into one goblet, to avoid confusion. Thaw two sexed semen straws at a time, at 35°C to 37°C for 45 seconds.
Load straws into pre-warmed AI guns, keep warm before depositing semen in uterine body. The insemination process should be completed within five mins, to minimise semen damage.