Retrospective study of factors affecting multiple ovulations, embryo recovery, quality, and diameter in a commercial equine embryo transfer program.

This research examines the factors influencing multiple ovulations, embryo recovery and quality, and embryo diameter in horses. It uses data analyzing different breeds, ages, and reproductive categories of 198 donor mares over a 10-year span of breeding seasons, using various forms and locations of artificial insemination.

Methodology

• The study involved 198 donor mares of different breeds, ages, and reproductive categories. These mares underwent insemination with fresh, cooled or frozen semen at an embryo transfer station and other artificial insemination centers.
• The researchers employed Pearson Chi-square test and logistic regression to analyze the results. This method was used in order to establish the factors impacting multiple ovulations, embryo recovery, embryo quality, and embryo diameter.

Results

• Out of 661 cycles, there were 937 ovulations documented. The study found that the average number of ovulations per cycle was approximately 1.42.
• The researchers found that the ovulation rate and occurrence of multiple ovulations were significantly influenced by the age, breed, and reproductive category of the mares.
• Embryo recovery occurred through uterine flushing between 7 to 10 days after ovulation, resulting in the extraction of 338 embryos; this equated to 51.1% embryos per cycle and 36.1% embryos per ovulation.
• The study uncovered that the factors affecting embryo recovery were the age and breed of the mares, reproductive category, the type of semen used, the number of ovulations, and the location of artificial insemination. However, the flushing protocol and day of flushing did not have an effect on embryo recovery.
• Finally, the factors that significantly impacted on embryo diameter were the mares’ age, the type of semen used, the number of ovulations, and the day of flushing. However, none of the factors studied affected the distribution of embryo quality.

Significance

• This study provides valuable insight into what influences multiple ovulations, embryo recovery and quality, and embryo diameter in equine species.
• The findings could enable the creation of optimized breeding strategies, improving the outcomes of equine reproduction via artificial insemination in the future.