A practical guide to estimate the age of the early CL by ultrasonography in mares examined for the first time to be used as recipients in a commercial embryo transfer program.

This research article discusses a study that sought to determine the accuracy of estimating the age of early Corpus Luteum (CL) in recipient mares for a commercial embryo transfer (ET) program. The study found that there was no significant difference in pregnancy or early embryonic loss rates when using this method versus daily ovulation checks.

Objectives

• The main objective of this study was to ascertain the accuracy of methods used to estimate the age of early Corpus Luteum (CL; the structure that develops in an ovary after an ovum has been discharged but degenerates after a few days unless pregnancy has begun) in mares that are being examined for the first time in a breeding season for use in a commercial embryo transfer program.
• This was done with the understanding that the echogenicity (the ability of a tissue to produce an echo) of the early CL changes in a notable way during the first five days of luteal development, presenting a potential way to estimate the age of the CL in mares that haven’t been frequently checked for ovulation diagnosis.

Methodology

• The researchers conducted a retrospective study, examining the post-transfer pregnancy rate and early embryonic loss in a total of 69 mares.
• They compared the results from 28 mares whose CL age was estimated at the first scan of the breeding season (with a minimum of 2 months gap since the previous examination) to results from 41 other mares whose ovulation day was determined through daily examinations. The latter group of mares also received an embryo on the identified day of ovulation.

Results

• The researchers found that there were no significant differences in both pregnancy and early embryonic loss rates when using the two different methods.
• The pregnancy rates observed were 85.7% and 85.3% for the group with an estimated CL age and the group with daily examinations, respectively.
• Similarly, the rates of early embryonic loss were equally close for both groups, listed at 12.5% and 11.4% respectively.
• These similarities in results were determined to be statistically insignificant with a listed p-value of greater than 0.1.

Conclusion

• The study concludes that estimating the age of early CL could be a reliable method in commercial embryo transfer programs, given that the observed rates of pregnancy and early embryonic loss were not significantly different from those resulting from daily ovulation checks.
• This presents a potentially more practical method for estimating the age of the CL in mares, especially those not frequently examined for ovulation diagnosis.