Effects of follicular ablation and induced luteolysis on LH and follicular fluid factors during the periovulatory period in mares.

This research investigated how induced-follicular waves affect LH concentrations and relevant follicular fluid factors in the ovulation process of mares. The study confirmed that while treatment caused an earlier increase in circulating LH, it had no impact on the concentrations of intra-follicular PGE, estradiol or progesterone in stimulated pre-ovulatory follicles.

Study Design and Methodology

• Fourteen mare’s oestrous cycles were monitored for the study, divided into control and treatment groups of seven each.
• The researchers implemented a cross-over design, with a one-cycle break when no treatments were applied between the treatment periods.
• In the treatment group, all antral follicles larger or equal to 8 mm were removed on day 10 post-ovulation. Following this, these horses received a luteolytic dose of PGF.
• Regardless of their group, all mares received a hormonal injection (1500 IU of hCG) once a follicle sized 32 mm or larger was detected (termed “Hour 0”). Follicular fluid was then aspirated 35 hours later.
• From day 10 until “Hour 0”, blood samples were drawn from each mare every 48 hours.

Results and Analysis

• Follicular fluid and blood plasma samples were assayed for concentrations of PGE, estradiol, progesterone, and luteinizing hormone (LH).
• A follicular wave was observed to follow follicle ablation in the treated mares, as predicted by the researchers.
• Concentrations of LH were verified to be higher in treated mares than in the control group (at a significance level of 0.05).
• However, concentrations of PGE, estradiol, and progesterone in the follicular fluid did not display a significant difference between the groups.

Study Conclusions

• Treatment was seen to cause an earlier increase in circulating LH. However, this treatment had no measurable effect on concentrations of intra-follicular PGE, estradiol, or progesterone in hCG-stimulated preovulatory follicles.
• This suggests that while induced follicular wave manipulation can impact LH concentrations, it does not influence the concentrations of other key hormones within the follicle itself during the ovulatory process.