Improved pregnancy rates from sexed semen

Carried out over a five-year period, the most comprehensive analysis of the performance of sexed semen in a commercial field setting ever undertaken has shown improvements in the pregnancy rates being achieved.

The results of this analysis was presented by ICBF and was based on over 1.82m conventional inseminations and 85,000 sexed semen inseminations from 2018 to 2022.

The analysis, which was undertaken by ICBF, Teagasc and the partner AI companies, indicated that the overall pregnancy rate from sexed semen on Irish dairy farms is now at 59%, compared with conventional AI at 64%. This indicates a relative pregnancy rate for sexed semen of 92%.

This is a significant improvement from the previous studies of sexed semen performance undertaken on Irish dairy farms in 2013, 2018 and 2019, which had all indicated that the relative pregnancy rate for sexed semen was approximately 84% of that achieved with conventional semen. However, each of these former studies were based on structured field trial data, whereas the current analysis is based on a statistical analysis of commercial field data.

The analysis focused solely on inseminations carried out by AI technicians from the partner AI companies – Dovea Genetics, Eurogene AI Services, Munster Bovine and Progressive Genetics – and pregnancy rates were validated against a subsequent birth event. No DIY AI inseminations were included in the analysis. Statistical analyses were undertaken of the field data, with important factors such as year, herd, parity, days in milk and cow genetic merit all accounted for in the model. Results from the study are summarised in Table 1 below.

Table 1: Summary of the performance of sexed versus conventional semen on Irish dairy farms

The results indicate that the relative performance over the five years was 92%, with incremental improvements in the technology also evident based on 2022 inseminations only (at 95% relative performance). This has been achieved through ongoing inprovements over the past five years including: improvements in the technology (i.e., sexed ultra); increases in the sperm concentration per straw (most straws now contain 4m sperm cells); and the establishment of two dedicated sexed semen labs here in Ireland, which has helped ensure greater uniformity of the sexed semen product and markedly increased the number of high EBI bulls available.

Another important outcome from the analysis was that when the raw phenotypic pregnancy rate was compared, then there was no difference in the pregnancy rates achieved by the sexed semen product compared with conventional AI (i.e., both had the same pregnancy rate). This occurred, the ICBF said, because sexed semen is being used selectively on heifers and the best fertility cows, with adherence to the strict protocols being promoted by Teagasc and the partner AI companies. As a result, the phenotypic pregnancy rates for the sexed semen is biased upwards, with this bias then getting accounted for in the subsequent statistical analysis.

While the results from the current analysis were positive, they also highlighted the need for strict adherence to the protocols associated with the use of sexed semen.

Positive results

Commenting on the analysis, Dr. Stephen Butler, Teagasc, noted that the results were an important outcome for dairy farmers using or planning to use sexed semen  this spring.

“In the past, the relative performance of sexed semen compared to conventional was seen as a big barrier to its potential usage by Irish farmers.

"The fact that the relative performance is now 92% and improving, should hopefully encourage more dairy farmers to consider using the product in their breeding programmes this spring."

Dr. Margaret Kelleher, ICBF, who undertook the overall analysis, noted that the analysis had once again highlighted the significant herd-to-herd variation in the performance of the technology.

“Like 2013, the difference in herd performance was striking with the top 10% and bottom 10% of herds achieving pregnancy rates for sexed semen of 73% and 40% respectively, with an average of 59%”.

She encouraged herd-owners to use the new sexed semen option as part of the ICBF HerdPlus sire advice tool, as this would make the job of selecting suitable cows and the subsequent breeding of the overall herd much easier from a herd-owner perspective.

Commenting on the results, Dr. Bernard Eivers, NCBC, noting that while the results were positive, it was critical that dairy farmers do not get complacent about the technology.

“Yes, the results are good, but as an industry, we need to continue to ensure that the technology gets applied correctly on farms, otherwise there will be disappointments."

That said, he encouraged those dairy farmers that have not yet tried the technology to consider it this breeding season, adding: “Our experience is that dairy farmers starting with the technology generally will try 10-15 straws, depending on their herd size, and we would encourage more farmers to adopt this approach this breeding season.”

Dr Andrew Cromie, GM for Sexing Technologies Europe thanked Margaret, Stephen and the partner AI companies for undertaking the seminal piece of work, adding: "It is a fantastic endorsement of the collaborative nature of the Irish cattle breeding industry, that this sort of comprehensive analysis, incorporating almost 2m insemination records, could be undertaken. The fact that dairy farmers can now have access to a technology that will help them address future challenges regarding dairy male calves, including also carbon inventories, is a significant step forward.”

This article first appeared on the ICBF website.