Effect of intrauterine saline infusion during the late luteal phase on the estrous cycle and luteal function of the mare.

The research tested the effects of saline solution infusion into horses during specific days after ovulation on their ovulation interval, luteal-life-span, and estrus duration. While the ovulation interval was unaffected, slightly shorter luteal-life-spans were observed on days 12 and 13. Simultaneously, the treatment had an immediate impact on the release of prostaglandin, with substantial releases taking place over the next 24 hours, directly affecting progestin levels.

Objective and Methodology

• The researchers aimed to examine the impact of intrauterine saline infusion on the reproductive cycle of mares, particularly the ovulatory interval, luteal-life-span, and duration of estrus. This was done by infusing warm sterile saline solution on days 12, 13, and 14 after ovulation and then comparing the effects to those of control mares.

Results on Ovulatory Interval and Luteal-life-span

• The infusion had no significant impact on the interval between ovulations. Conversely, on days 12 and 13 following ovulation, it reduced the luteal lifespan compared to controls. However, on day 14, the reduction in luteal lifespan was insignificant.

Results on Interval from Corpus Luteum Regression to Ovulation and Estrus Duration

• The study found no significant effects on the interval from corpus luteum regression to ovulation, or the final follicular phases, with the averages for treated mares on days 12 and 13 matching closely with those of controls.
• Similarly, the duration of estrus, or the sexual heat period, remained essentially unchanged. Though slightly shorter for treated mares (5.1 days) versus controls (6 days), this difference was deemed insignificant.

Effects on Prostaglandin Release and Progestin Concentrations

• The intrauterine saline infusion triggered an immediate release of prostaglandin F(2alpha) within 5 minutes. Further sizeable releases took place over the next 24 hours, illustrating that this treatment significantly influences the production of this hormone, which plays a key role in the reproductive process.
• Consequently, progestin concentrations dropped rapidly in response to the release of prostaglandin. This highlights a direct relationship between the procedural intervention and shifts in reproductive hormone levels.