Field fertility of sex-sorted and non-sorted frozen-thawed stallion spermatozoa.

This research compares the fertility rate of sex-sorted and non-sorted frozen stallion sperm, concluding that the low fertility might be due to the low-dose insemination conditions with frozen-thawed, not because it is sex-sorted.

Research Methodology

• The research was conducted in the 2004/2005 breeding season. The sperm used for the research was sourced from two Hannovarian stallions.
• A hysteroscopic insemination technique was employed, a method that deposits low doses of frozen-thawed sex-sorted (SS) or non-sorted (NS) sperm onto the utero-tubal junction.
• The sperm was deposited at the indicated times (32 or 38 hours) after the administration of Chorulon, a medication used to induce ovulation.
• The doses of the sperm varied – 6, 13, or 25 x 10(6).

Research Findings

• The research yielded low fertility rates, with only one successful pregnancy from artificial insemination with frozen SS sperm out of 29 cycles.
• Two pregnancies were obtained when mares were inseminated with 6 x 10(6) NS sperm in 31 cycles.
• Mares that failed to conceive after two experimental cycles had to be allocated to a conventional insemination group.
• Insemination with higher (> 500 x 10(6)) doses of motile NS frozen-thawed sperm yielded satisfactory conception rates (35.5%).

Analyzed Results and Suggestions

• The satisfactory conception rates from the higher dose insemination suggest that the quality and viability of the frozen semen were acceptable.
• However, the low fertility observed after hysteroscopic insemination with low doses of sex-sorted or non-sorted sperm highlighted potential issues with the technique.
• The researchers suggested that the poor fertility might be primarily linked to the low-dose insemination conditions with the frozen-thawed sperm is rather the reason instead of it being sex-sorted.