The use of synthetic prostaglandin analogue to induce oestrus in mares.

This research paper investigates the effectiveness of fluprostenol, a synthetic prostaglandin analogue, in inducing estrus in mares. The study observes successful estrus induction in around 73.3% of cases following the first injection, with 40% of these mares conceiving during the first induced estrus.

Objective of the research

• The primary objective of the study was to evaluate the clinical efficacy of fluprostenol, a synthetic prostaglandin analogue, in treating mares in extended dioestrus. This treatment aimed at inducing oestrus in these horses.

Research methodology and findings

• A clinical trial was conducted involving 359 mares, which were grouped into different categories – ones which had abortion or reabsorption of the conceptus during the first 150 days of pregnancy, pseudopregnant mares, lactating mares without regular estrous cycles, and barren and maiden mares without cycles during the breeding season.
• The mares were treated with 250 micrograms of fluprostenol. If no signs of estrus were observed within five days of the first injection, another dose was administered.
• The study found that 73.3% of the mares displayed signs of oestrus within five days of the first injection, and 40% of these mares were found to be pregnant during the first induced oestrus. Additionally, 8.1% responded to a second injection with successful estrus.
• However, some mares remained unresponsive to treatment, with 35 showing signs of estrus 7-23 days after the second injection. Overall, 51.5% of the mares conceived after therapy.

Progesterone levels analysis

• Before treatment, plasma progesterone levels were measured. It was revealed that 80.3% of the mares had progesterone levels greater than 1 ng/ml, suggesting the presence of functional luteal tissue in their ovaries.
• The highest proportion of progesterone was found in lactating animals.
• About 16.5% of those mares with progesterone levels less than 1 ng/ml responded to treatment on the first attempt, but some mares were unresponsive to fluprostenol even though they had lower progesterone levels.

Conclusion

The results of this study affirm previous observations that most non-pregnant mares which failed to cycle during the breeding season were in a condition of extended dioestrus rather than anestrus. The findings also demonstrate the clinical effectiveness of fluprostenol in inducing estrus in these mares.