A retrospective study of artificial insemination of 251 mares using chilled and fixed time frozen-thawed semen.

The research article presents a comparative study on the efficiency of artificial insemination in mares using chilled and frozen semen over two breeding seasons, the results suggest that frozen semen leads to a higher conception rate.

Objective

The purpose of this study was to test the belief that artificial insemination (AI) using chilled semen produces a higher rate of conception in mares than AI with frozen semen.

Methods

• The study was retrospective and covered the 2006 and 2007 northern hemisphere breeding seasons.
• A total of 251 mares were artificially inseminated with either chilled (112) or frozen (139) semen.
• The timing of insemination was determined through per rectum ultrasonography of the mare’s reproductive tract.
• A hormone, deslorelin acetate, was used to induce ovulation in the mares.
• A single preovulatory dose of the chilled semen was delivered into the mare’s uterine body.
• The frozen semen was administered in two doses, one before and one after ovulation, by using a deep uterine insemination technique.
• Pregnancy was detected ultrasonographically 15 days after insemination.

Results

• The use of frozen semen produced a significantly higher conception rate (82.0%) as compared to the use of chilled semen (69.6%).
• The difference in conception rates was statistically significant (P = 0.022).

Conclusions

• The study thus contradicts the traditional belief that frozen semen results in lower fertility rates in mares, the data gathered indicates that the use of frozen semen can indeed achieve conception rates equal to or higher than those achieved with chilled semen.
• Therefore, the findings of this research expand the available options for stallion selection for mare owners.