Effects of the Prostaglandin F2α Analogues Cloprostenol and Luprostiol in Combination With hCG on Synchronization of Estrus and Ovulation in Mares

- We evaluated differences of two PGF2α analogues in combination with human chorionic gonadotropin (hCG) in cyclic mares.
- Time to estrus and ovulation was equal for luprostiol and d-cloprostenol.
- Induction of ovulation was more reliable in luprostiol-induced cycles.
- Fertility was not impaired by either PGF2α analogue in combination with hCG.

The aim of the study was to evaluate differences between two PGF2α analogues-luprostiol and d-cloprostenol-in combination with human chorionic gonadotropin (hCG) in their ability to induce estrus and ovulation and their impact on fertility. Breeding records of 155 mares (in 274 estrous cycles) were analyzed. Luteolysis was either induced with luprostiol (group LUP, 3.75 mg i.m.) or d-cloprostenol (group CLO, 30 μg i.m.) or mares came into estrus spontaneously (group CON). Ovulation was induced in all cycles by injection of hCG (1,500 IU i.v.). There was no significant difference between LUP and CLO in the interval from induction of luteolysis to injection of hCG (LUP: 4.4 ± 0.3 days, CLO: 5.1 ± 0.3 days) and from induction of luteolysis to ovulation (LUP: 6.5 ± 0.4 days, CLO: 7.2 ± 0.4 days). The time from injection of hCG until detection of ovulation was shorter in LUP than in CLO and CON (LUP: 2.2 ± 0.2 days, CLO: 2.8 ± 0.2 days, CON: 2.5 ± 0.1 days, CON and CLO vs. LUP P < .01). The percentage of cycles in which ovulation occurred within 48 hours after induction of ovulation was higher in LUP than in CLO and CON cycles. Pregnancy rate was not affected by either treatment. In summary, induction of estrus with luprostiol leads to a better synchronization of ovulation after treatment with hCG than cloprostenol without impairing fertility.