The effect of mare’s age on multiple ovulation rate, embryo recovery, post-transfer pregnancy rate, and interovulatory interval in a commercial embryo transfer program in Argentina.

The research paper studies the effects of the age of mares on various reproductive parameters within a commercial equine embryo transfer program. The study revealed that younger and middle-aged mares had a higher embryo recovery rate, while older mares had higher chances of multiple ovulations. The pregnancy rate was not significantly affected by age. The length of the interovulatory intervals differed, with older mares having longer intervals than younger and middle-aged mares, and was influenced by various factors such as individual mare, age, day of flushing, and month.

Research Methodology and Classification

• The study involved grouping mares into three categories based on age: Group 1 comprised 3 to 4-year-old fillies, Group 2 consisted of middle-aged mares between 5 to 10 years old, and Group 3 contained older mares aged between 13 and 25 years old.
• The team of researchers compared various reproductive parameters such as the embryo recovery rate, multiple ovulation rates, pregnancy rates, and interovulatory intervals across these three groups.

Findings

• Embryo recovery rate: Groups 1 and 2 demonstrated higher embryo recovery rates compared to Group 3. Specifically, 70.1% of Group 1 and 71.6% of Group 2 had higher embryo recovery rates, compared to 54.9% for Group 3.
• Multiple ovulation: Older mares (Groups 2 and 3) were noted to be more likely to have multiple ovulations compared to younger mares, by 2.5 and 3.4 times respectively.
• Pregnancy rate: The effect of age group on pregnancy rate was not substantial, indicating age is not a significant factor influencing the pregnancy rate in mares.
• Interovulatory intervals: The length of time between ovulatory events was influenced by the individual mare’s age, the day of flushing, and the month. Older mares (Group 3) showed longer interovulatory intervals than Groups 1 and 2.

Implications of the Study

• The research contributes valuable insights to understanding the impact of age on the reproductive capability of mares, especially in a commercial embryo transfer setting.
• The results can be applied to optimize the operation of horse breeding programs, leading to more efficient and cost-effective practices and procedures.