Does Clinical Treatment with Phenylbutazone and Meloxicam in the Pre-ovulatory Period Influence the Ovulation Rate in Mares?

The research article explores the effects of non-steroidal anti-inflammatory drugs (NSAIDs) like meloxicam and phenylbutazone on ovulation in mares. The study found that the use of these NSAIDs during the pre-ovulatory period majorly impedes ovulation, possibly by causing intrafollicular hemorrhage and luteinization of anovulatory follicles.

Study Purpose and Methodology

• The research aimed to determine how NSAIDs, in particular meloxicam and phenylbutazone, impact the development of pre-ovulatory follicles in mares and ultimately, ovulation.
• 11 mares were used in the study. They were examined over three consecutive oestrous cycles using gynaecological and ultrasound inspections performed every 12 hours.
• Once follicles of 32-mm diameter were detected, deslorelin was administered to induce ovulation. The first cycle served as a control in which only deslorelin was administered.
• In the next two cycles, both deslorelin and either phenylbutazone or meloxicam were administered to the mares until ovulation or the onset of follicular bleeding.

Findings and Implications

• The induction of ovulation after administering deslorelin in the control cycle occurred between 36-48 hours for all the mares.
• In contrast, in the cycles where NSAIDs were administered, ovulation was significantly impeded. In the meloxicam cycle, 10 out of 11 mares (92%) didn’t ovulate, and in the phenylbutazone cycle, 9 out of 11 mares (83%) didn’t ovulate.
• The ultrasound showed the presence of hyperechoic spots suggestive of haemorrhagic follicles in both treatment cycles, which illustrates that these drugs can induce intrafollicular hemorrhage.
• Considering these findings, the research suggests that administering NSAIDs like meloxicam and phenylbutazone at therapeutic doses can lead to follicular luteinization and ovulatory impairment in mares.
• These conclusions are crucial because they highlight a potential avenue wherein the application of NSAIDs might end up causing negative impacts on reproductive activity—especially in animals intended for breeding.