Sexed semen usage can increase dairy herd genetic gain, which in turn, can deliver better financial return to farmers when it is used effectively.
This message was reiterated at the Teagasc National Dairy Conference at one of the workshops where Prof. Stephen Butler, Dr. Stuart Childs and Dr. John McCarthy spoke about its worth on farm systems, and how to effectively implement it.
The message was clear and simple – that sexed semen allows for the highest genetic merit females within the herd to produce replacements with increased milk solids production potential, with a lower carbon footprint.
This method then leads to the reduced number of low value dairy bull calves, as less dairy straws are required to generate the heifer replacements, and more females can be bred to high Dairy Beef Index (DBI) sires.
However, as the breeding season for the autumn calving herds is only a few weeks away, it is important to be aware of the most cost-effective strategies to integrate sexed semen into dairy breeding to achieve high conception rates.
Sexed semen
The average conception rate to sexed semen is slightly less than conventional semen – the relative conception rate over 90%.
Conception rates with sexed semen continue to improve and will further increase the uptake of the technology.
The improvement in conception rate is a combination of farmers getting a better understanding of the product and that the technology itself is constantly being advanced.
When you are picking bulls, the same rules apply for both sexed and conventional, making sure to use a large team of bulls and a selection of bulls that will enhance the areas that need improving in your herd.
For the cows that you are breeding off, breed off the best genetics, the top 50% of the herd.
For your cows, breed off cows with the following:
- Parity one to four;
- Over 50 days in milk on day of artificial insemination (AI);
- BCS of over three;
- Ensure they are cycling regularly;
- Ensure they have no postpartum disorders or uterine disease.
For your heifers, make sure to target their live weight and that they have a body condition score (BCS) of over 3.25, while ensuring that they are cycling regularly.
Timing of AI
The timing of insemination is paramount to the successful conception of sexed semen and it should ideally be used in the first three weeks of the breeding season or within the first 10 days, if possible.
Timing of AI is more critical for sexed semen compared to conventional and for maximum success, AI with sexed semen should take place 14-20 hours after the onset of heat.
The problem with this is, that for farmers without collars or heat detection devices, it can be very difficult to pin-point the first onset of heat.
This challenge can be overcame by using fixed-time AI, as even though the initial cost of approximately €25/animal is often seen as prohibitive, it is counterbalanced by the compact calving and having cows more days in milk.
Fixed-time AI eliminates any of the risk involved with sexed semen, and will ensure all sexed semen is used at the start of the breeding season, and mitigate any risk of reduced conception rate impacting on six week calving rate the following season.
The following fixed-time AI eight-day protocol is recommended for dairy replacement heifers:
In order for fixed-time AI protocol to be successful, it is critically important that all interventions take place on the appropriate days and at the correct times.
The following 10-day fixed time AI protocol for dairy cows is recommended:
Any errors or non-compliance with the protocol can severely impact the fertility of the animal at the time of insemination, and so careful planning and organisation of the protocol is critical to its success.
Handling of straws
The handling of sexed semen straws is crucial to its success, as once the straws are thawed, they have to be used in a matter of minutes.
The recommendation is to organise sexed straws into one goblet for easy access and to only thaw two sexed semen straws at a time.
Straws should be thawed at 35-37℃ for 45 seconds and then loaded into a pre-warmed AI gun, which should be kept warm for the duration of AI.
Deposit the semen in the uterine body and make sure the inseminations are completed within five minutes to maximise the performance of sexed semen usage.