We are now into the breeding season and, for the majority of dairy farms, sexed semen usage is going to dominate the first three weeks of artificial insemination (AI).
Conception rates with sexed semen have been improving year-on-year, which is due to farmers’ efficient usage of the product and the advancement of the product recently.
However. a refresher on the timing of AI sexed semen is always welcome, as most dairy straws are up at €50/straw, which means the timing of AI to maximise conception rates is crucial for an efficient and cost-effective breeding season.
On top of that, many farmers are only rearing the amount of heifers they need, with a selection of females getting sexed semen and the rest going to dairy-beef.
This method runs the risk of not breeding enough heifers to fulfill your replacement rate target and, with the looming shortage of dairy heifers in the coming years, it might be no harm to produce surplus heifers rather than run tight.
This potential shortage of dairy heifers means that buying in heifers to make up a shortage of your own is going to be costly, and producing surplus may be profitable as the heifers may be heavily sought after.
Timing of sexed semen
<p>It is important to remember that sexed semen is a damaged product, as the sperm cells are damaged during the sorting process, which means the viability of the sex-sorted sperm cells in the reproductive tract is shorter (less than 12 hours) than for conventional (over 24 hours).
So, the timing of sexed semen is a bit more tricky to get right, and will require more accurate heat detection along with possibly serving cows at least twice a day.
When heifers and cows are being inseminated with sexed semen, AI should be conducted 14-20 hours after their observed heat.
If AI is being conducted once a day, some dams will be at the optimum time for sexed semen, and all other should receive conventional straws.
However, when AI is carried out twice daily, most dams will be at the optimum time for sexed semen either in the morning or evening.
If you carrying out AI at 7am each morning, the suitability for cows after observed heat as per Teagasc is as follows:
| First observed heat | Hours since heat onset at 7am | Suitabaility for sexed semen</th> | |
|---|---|---|---|
| 6:00a.m. | 1hr | 0% | 50% |
| 10:00a.m. | 21hr | 100% | 50% |
| 2:00p.m. | 17hr | 100% | 100% |
| 6:00p.m. | 13hr | 75% | 100% |
| 10:00p.m. | 9hr | 25% | 100% |
As you can see from the table above, carrying out AI once a day would not suit using 100% sexed semen but can work when using conventional semen as well.
Many farmers opt to completely use sexed semen for the first couple of weeks of the breeding and this will require AI taking place twice daily, once in the morning and again about eight hours later, that evening.
If you carrying out AI at 3pm each evening, the suitability for cows after observed heat as per Teagasc is as follows:
| First observed heat | Hours since heat onset at 7am | Suitabaility for sexed semen</th> | Suitability for conventional |
|---|---|---|---|
| 6:00a.m. | 9hr | 25% | 100% |
| 10:00a.m. | 5hr | 0% | 75% |
| 2:00p.m. | 1hr | 0% | 50% |
| 6:00p.m. | 21hr | 100% | 50% |
| 10:00p.m. | 17hr | 100% | 100% |
For some farmers looking to get the best out of their sexed semen, they may AI cows multiple times a day and base it purely on the onset of heat, not being fixed to the two times used in above example.
However, the above example will allow for cows in the herd to be suitable for AI over 80% of the time.
If farmers are willing to AI throughout the day, then they can take a more flexible approach that allows them to get cows at optimal times almost 100% of the time.
For successful outcomes with sexed semen, farmers need to follow the timing of AI as per Teagasc, as follows:
- Onset of heat between 1:00p.m. and 7:00p.m.: AI at 9:00a.m. next morning;
- Onset of heat between 4:00p.m. and 10:00p.m.: AI at 12 noon the next day;
- Onset of heat between 7:00p.m. and 1:00a.m: AI at 3:00p.m. the next day;
- Onset of heat between 10:00p.m. and 4:00a.m: AI at 6:00p.m. the next day;
- Onset of heat between 1:00a.m and 7:00a.m: AI at 9:00p.m. that night.
This observation of heat and timing of AI can be eliminated through a synchronisation programme, which if all injections are administered at correct times, a farmer will achieve a 100% submission rate with a high conception rate.
Fixed timed AI is worth the money and should be used if submission rates followed by conception rates have been poor, but if effective timing of AI and efficient heat detection has been working on the farm, farmers should stick these guidelines to maximise their conception rates with sexed semen.
