The effect of dexamethasone and flunixin-meglumine on ovulation, endometrial oedema, and inter-ovulatory interval length in the mare.

This research investigates the impact of the drugs dexamethasone and flunixin-meglumine on ovulation, endometrial oedema, and the interval between ovulations in mares. The study found that flunixin-meglumine can cause high rates of ovulation failure and anovulatory follicles, while dexamethasone did not block or delay ovulation, yet increased the interval between ovulations.

Objectives and Methodology

The study aimed to explore how the drugs flunixin-meglumine (a non-steroidal anti-inflammatory drug) and dexamethasone (used to prevent persistent mating-induced endometritis) affect ovulation, endometrial edema, and the length of the inter-ovulatory interval in mares. This involved monitoring six mares over four consecutive cycles using a crossover design.

• The mares were treated with hCG, a hormonal trigger that stimulates ovulation, and then randomly assigned to one of four groups.
• Group FM was treated with flunixin-meglumine 24 and 36 hours after hCG administration.
• Groups DEX1 and DEX2 were treated with dexamethasone at the 24-hour mark, with DEX2 receiving an additional dose at the 36-hour mark.
• Group CON received no further treatment as a control group.

Results and Key Findings

The research primarily focused on ovulation and HAF rates, endometrial oedema profiles, and the inter-ovulatory intervals (IOI).

• It was found that all mares in both the control and dexamethasone groups ovulated normally without the formation of any haemorrhagic anovulatory follicles (HAF).
• Mares in group FM, treated with flunixin-meglumine, however, showed a high rate of ovulatory failure, with 83% developing a HAF.
• Endometrial oedema scores were lower when dexamethasone was administered, suggesting the drug was more effective at reducing endometrial oedema than flunixin-meglumine.
• The inter-ovulatory intervals for mares treated with dexamethasone (both DEX1 and DEX2) were longer than those from the control and FM groups.

Conclusion

The research concluded that dexamethasone, whether administered once or twice during the critical window of hCG-induced ovulation, doesn’t block or delay ovulation. Instead, it results in similar ovulation rates as untreated control mares. However, it was noted that the inter-ovulatory intervals of dexamethasone-treated mares were longer than those untreated or treated with flunixin-meglumine. Dexamethasone proved more effective in reducing endometrial oedema than flunixin-meglumine.