The effect of the interval from PGF treatment to ovulation on embryo recovery and pregnancy rate in the mare.

The research evaluates the impact of the time interval between the application of Prostaglandin (PGF) treatment and ovulation on the fertility rates of mares (female horses) in two different farms. The study, carried out over seven breeding seasons, deduces that a shorter interval between PGF treatment and ovulation tends to reduce fertility.

Research Methodology

• The study was conducted in two separate farms covering 513 estrous cycles of 215 mares on farm 1 and 375 embryo flushing procedures in 65 donor mares on farm 2.
• For artificial insemination, frozen/thawed semen was used on farm 1, while fresh semen was used on farm 2.
• Prostaglandin (PGF2α) analogues were used to induce estrus in 179 out of the overall cycles on farm 1, and artificial insemination following PGF-induced luteolysis was applied in 327 cycles on farm 2.

Results and Analysis

• Data from the two farms was divided into three groups based on the interval from PGF treatment to ovulation (ITO): less than 6 days, 6 to 8 days, and greater than 8 days.
• A regression model was used to analyze the effect of various factors on both pregnancy rate (PR) and embryo recovery rate (ERR) of the mares.
• Out of all factors, the ITO was the one to induce significant influence on both ERR and PR, as indicated with a P value less than 0.05.
• In Farm 1, mares with an ITO of less than 6 days, 6-8 days, and more than 8 days were observed to have PRs of 26.6%, 39.4%, and 55.9% respectively. The mares which were inseminated post spontaneous luteolysis (without PGF treatment) recorded a PR of 42.5%.
• In Farm 2, mares with the same ITO groups had ERRs of 55.%, 62.6%, and 73.7% respectively. Mares flushed after a spontaneous estrus had an ERR of 75%.

Conclusion

• The time interval between PGF treatment and ovulation had a significant impact on both ERR and PR in mares, with a shorter ITO reducing fertility rates.