Use of progesterone in microspheres for maintenance of pregnancy in mares.

This study explores the effectiveness of administering progesterone encapsulated in microspheres to maintain pregnancy in mares following induced luteolysis. It found higher concentrations of this treatment to be most effective, particularly 2.25 g doses.

Research Objective

• The primary goal of this research was to evaluate progesterone delivered in poly(d-,l-lactide) microspheres as a treatment to sustain pregnancy in mares. Specifically, the research examined the effects of this treatment after inducing luteolysis — the regression of the corpus luteum in the mares — with a chemical named prostaglandin F2 alpha on day 14 of pregnancy.

Research Methodology & Experimental Setup

• Four groups of mares were used in this study. One group (six mares) received a vehicle treatment and served as the control, while the other three groups were respectively administered with 0.75 g (seven mares), 1.5 g (eight mares), and 2.25 g (five mares) of progesterone enclosed in microspheres on pregnancy days 12 and 22.
• Pregnancy was confirmed, and the progress was monitored, by performing transrectal ultrasonography every other day.
• The researchers also kept track of serum progesterone concentrations on a daily basis.

Research Findings

• Results indicated that a significantly larger number of mares that received 1.5 g or 2.25 g of progesterone (6 out of 8 and 4 out of 5 mares, respectively) were able to maintain pregnancy through day 32, as compared to the control group mares (zero out of six) or those that received 0.75 g (three out of seven).
• Progesterone levels were found to decline significantly in all groups post administration of prostaglandin F2 alpha on day 14, and substantial effects of the treatment and time on progesterone levels were noted between days 12 and 22, as well as between days 22 and 32.
• While the treatment with 1.5-g and 2.25-g doses of encapsulated progesterone improved the chances of maintaining pregnancy compared to the vehicle-treated control group, the highest efficacy was observed with the 2.25 g dose of the encapsulated progesterone.

Conclusion

• The study concluded that progesterone, when administrated in higher concentrations (specifically 2.25 g) enclosed in microspheres, could be a successful treatment for maintaining pregnancy in mares following induced luteolysis.