Hormone supplementation protocol using estradiol benzoate and long-acting progesterone is efficient in maintaining pregnancy of anovulatory recipient mares during autumn transitional phase.

This study investigates if the use of estradiol benzoate and long-acting progesterone can support continued pregnancies in female horses who are not ovulating, during the autumn transitional period. The results suggest this hormonal supplementation may increase the rate of successful pregnancies in these circumstances.

Research Context

• This research paper focused on the maintenance of pregnancy in anovulatory recipient mares (female horses) during the autumn transitional period. The autumn transitional period is a phase where mares tend to be subfertile due to changing photoperiods, leading to instability in ovarian activities.
• The researchers sought to determine whether hormone supplementation with estradiol benzoate and long-acting progesterone could be effective in maintaining pregnancies that have been initiated through embryo transfer.

Study Design and Participants

• 76 mares were involved in the study. 40 received the hormonal treatment (treated group), while the remaining 36 formed the control group.
• The control group comprised mares with regular estrous cycles, capable of ovulating on their own, and had an embryo transferred 5 days after ovulation. They did not receive any hormonal supplementation.
• In the treated group, the administration of hormones started 8 days before the embryo transfer. The mares received diminishing doses of estradiol benzoate over 3 days and a sizable dose of long-acting progesterone 5 days after ovulation, repeated on the day of embryo transfer and every 7 days until 120 days of gestation.

Hormonal Treatment Protocol

• Estradiol benzoate and long-acting progesterone were used for hormonal supplementation. The protocol comprised of decreasing doses of estradiol benzoate administered over 3 days, followed by substantial doses of long-acting progesterone from Day 5 post-ovulation and continued at regular intervals.

Outcome Measures

• Pregnancy diagnoses were conducted on Days 13, 30, and 60 of the gestation period.
• The mares were also classified based on their suitability for embryo transfer: acceptable, marginally acceptable, or unacceptable. Similar evaluations were carried out for the quality of embryos too.

Results and Conclusion

• The results showed a significantly higher pregnancy rate in the group that received hormonal treatments than the control group.
• The suitability of mares or quality of embryos did not impact the success rates of pregnancy.
• Therefore, the study concludes that estradiol benzoate and progesterone supplementation can successfully uphold pregnancies in anovulatory recipient mares during the autumn transitional period.