Control of estrus with prostaglandin F2alpha in mares: minimal effective dose and stage of estrous cycle.

This research aimed to identify the minimal dose of a specific hormone (prostaglandin F2alpha) that can effectively suppress estrus (a period of sexual receptivity) in horses, and figured out the effectiveness of the hormone at various stages of the horse’s sexual cycle.

Understanding the Objective

• This research focused on understanding the effect of different doses of a hormone called prostaglandin F2alpha (PGF2alpha) on the estrus cycle in mares. The hormone was given subcutaneously (under the skin).
• The study looked to determine the minimal dose of the hormone that could effectively cause luteolysis (the breakdown of the corpus luteum, which signals the end of the estrus cycle) ensuring sufficient hormonal balance for mares’ health.

Methodology

• PGF2alpha was administered in varying doses (2, 3, 5, and 10 milligrams) to mares of mixed breeding with an average body weight of 400 kilograms.
• The doses were given from 7 to 9 days after ovulation, to see the effect of these doses on the post-ovulation phase of the estrus cycle in mares.

Findings

• It was observed that low doses (2 and 3 milligrams) of PGF2alpha could cause luteolysis in some mares. However, in doses of 5 or 10 milligrams, the hormone was able to cause luteolysis in all mares, confirming that these higher doses have a definite effect.
• The 10-milligram dose did not cause luteolysis in mares who were only 1 day past ovulation, and only had this effect on 2 out of 5 mares on the 3rd day past ovulation.
• However, when administered 5 or 7 days after ovulation, the 10-milligram dose was effective in causing luteolysis in all mares tested.

Conclusion

• The study concludes that the minimum effective dose of PGF2alpha needed for luteolysis is about 9 μg/kg.
• Furthermore, the study found that PGF2alpha is effective from day 5 post-ovulation. This suggests that its administration should be timed appropriately for maximum effectiveness during the estrus cycle of mares.