How to improve conception rates using sexed semen
Farmers need to be more dedicated to observing the onset of heat when using sexed semen for it to pay off, new research shows.
Timing of artificial insemination is critical, and farmers need to be much more dedicated to observing the onset of heat when using sexed semen, according to Teagasc Researcher Stephen Butler, speaking at the recent National Dairy Conference.
A recent Teagasc conducted study found sexed semen to have a relative conception rate of 76pc compared to conventional semen, according to Stephen. However, if the onset of heat was more strictly observed and the timing of AI was closer to the time of ovulation, this could improve conception rates.
A field trial using lactating dairy cows was conducted in 2018 to compare the fertility performance of conventional semen versus sexed semen (sexed ULTRA 4M).
The conception rate was 59.9pc for conventional semen and 45.5pc for sexed semen, resulting in a relative conception rate of 76pc (sexed semen compared to conventional), according to the Moorepark based Researcher.
In the study, ten bulls were identified to produce conventional and sex-sorted semen straws. Of the 10 bulls, four were located in a bull stud at nearby the sorting laboratory.
In Ireland six bulls were selected for inclusion in the trial, with ejaculates being directly transported from the Irish bull stud to the lab in the UK, roughly a six door to door trip, according to Stephen.
The findings of the study showed that cows inseminated with conventional semen had a mean conception rate of 59.9pc versus 45.5pc for cows inseminated with sexed semen, according to Stephen. The relative conception rate in this study was 76pc.
In the current study, farmers identified the cows in heat, and the AI technician randomly allocated conventional and sexed straws to the cows that were presented for insemination, according to Stephen.
Since this study was conducted, preliminary results from a similar study in New Zealand comparing conventional and sexed ULTRA have emerged, reporting a mean relative conception rate of 75pc according to Stephen.
Some recent studies have shown more that there was a better relative conception rate in herds using sexed semen in indoor systems, according to Stephen. He said that this may be because of better AI timing.
The expected lifespan of conventional semen in the female reproductive tract is roughly 24h, but much shorter for sexed semen, therefore the timing of AI is much more critical for sexed semen, he said.
He concluded that inseminations with sexed semen should be conducted close to the time of ovulation. It is likely, therefore, that studies reporting 90pc relative conception rate in confinement systems are a result of better timing of AI relative the time of ovulation because most cows are bred using fixed-time AI synchronization protocols.
Sex-biased semen is a technology that provides many potential advantages for the Irish dairy industry, according to. These include;
· Reduce the number of male dairy calves;
· Provide opportunities to increase the value of beef output;
· Streamline heifer rearing;
· Improve biosecurity in expanding herds.
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