First field results on the use of stallion sex-sorted semen in a large-scale embryo transfer program.

This study showcases the usage and effectiveness of stallion sex-sorted semen in a large-scale equine embryo transfer program, measuring its efficiency and precision, resulting in a sex accuracy of 90.3% and an overall efficiency of 39%.

Methodology

• The research was conducted during the 2009, 2010 and 2011 breeding seasons, across 938 synchronized breeding cycles which were artificially inseminated.
• Out of these, 100 mares did not ovulate resulting in 838 usable cycles. These cycles utilized 887 doses of sexed semen, averaging 1.06 doses per cycle.

Results

• From the 838 flushings performed, about 51.9% resulted in recovery of at least one embryo, with a total of 496 embryos being recovered, which includes twins and triplets.
• The pregnancy rate at 25 days was 81.5%. This was calculated based on one embryo transferred per recipient.
• There was no significant statistical difference found in embryo recovery between mares inseminated before or after ovulation, or when the quantity of sexed sperm per dose was increased from 15 million to 45 million.
• The researchers noted a wide variation in embryo recovery rate between different stallions in the study.
• Using ultrasound fetal sex determination, the sex accuracy of the sex sorting was found to be 90.3%.
• The overall efficiency, calculated as female embryo pregnancies per usable cycles, was 39%. This implies that to achieve a female pregnancy of at least 75 days, it was necessary to perform 2.5 flushing processes.

Significance

• This study demonstrates the practicality and effectiveness of using stallion sex-sorted semen in large-scale equine embryo transfer programs.
• The data shows promising results, with high sex accuracy and relatively high overall efficiency, making the method cost-effective and time efficient, while offering more controlled breeding outcomes.