Kinetic studies and production rate of equine (e) FSH in ovariectomized pony mares. Application to the determination of a dosage regimen for eFSH in a superovulation treatment.

The research paper is about a study performed to determine the effective dosage of equine FSH (eFSH) in a superovulation treatment for pony mares. The study used a kinetic approach examining rates of hormone production and elimination, and found that a dosage of 2.2 micro g/kg three times a day provided satisfactory results.

Objective and Methodology

• Researchers set out to determine the most effective dosage and frequency for administering eFSH as part of a superovulation procedure in pony mares. They aimed to do this by examining the production rates and kinetic parameters of elimination for the hormone.
• Four ovariectomized pony mares were sampled every 10 minutes for 8 hours during the breeding season to measure eFSH production rates. The kinetics parameters on the other hand, were determined by assigning four different dose levels of eFSH to the same mares using a randomized 4×4 Latin Square protocol. The administered dose levels included 4.4, 8.8, 17.6, and 35.2 micro g/kg.

Findings and Interpretation

• The researchers found that the mean plasma clearance was about 0.256 ml.kg(-1).min(-1) and was independent of the dose. The time the hormone stayed in the body ranged from 5.5 to 10.8 hours and increased with the dose.
• The estimated FSH production rates ranged from 8.6 to 15.3 micro g.kg(-1).day(-1), which equals about 2.89 to 3.45 mg per day per mare.
• Two dosage regimens were then tested on cyclic mares. The first was 3.45 mg per day (4.4 micro g/kg three times a day) which corresponds to the maximum daily production rate of the hormone in ovariectomized mares, and the second was 1.72 mg per day (2.2 micro g/kg three times a day) which is half of that production rate.
• Researchers found the second dosage regimen (2.2 micro g/kg three times a day) produced satisfactory results in terms of the number of ovulations and embryos and had fewer unwanted effects such as luteinized or anovulatory follicles.

Conclusion

• These findings suggest that a dosage regimen of 2.2 micro g/kg three times a day is effective for superovulation treatment in pony mares with minimal side effects.
• This study could guide future practices by providing a model for determining effective dosage regimens based on the kinetic parameters of eFSH production and elimination.