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Foreseeing Thoroughbred's Matings Result by Analyzing Dismounted Semen Samples

This article is written based on a research article (Link). The "iSperm® Equine portable device" mentioned in the article is the iSperm mCASA. With the iSperm, your breeding work will be much easier. Check out https://www.isperm.co/ or Contact us for the details.


Why is the likelihood of pregnancy prediction essential in the Thoroughbred breeding industry?

All registered Thoroughbreds must be bred through live cover, demand on The Jockey Club. In The Jockey Club’s Principal Rules and Requirements of The American Stud Book, it is stated that artificial insemination is “expressly prohibited.” While the fertility of Thoroughbreds is low, with a per cycle conception (PCC) rate of around 60-69%, the likelihood of pregnancy is important to be predicted to increase the efficiency during the breeding season. A mare can be re-mated directly during the estrous cycle without waiting for the next estrous cycle, managing the reproductive performance of Thoroughbred horses in the breeding season.

What to do to determine the probability that pregnancy will occur from a cover?

Detailed and advanced dismount semen sample analysis from Thoroughbred stallions could be applied to foresee the likelihood of a given mating. Besides of the analysis of the semen quality, several aspects might affect the result of the live cover, which are the ages of the Thoroughbred mare and stallion, the former breeding records, mating and ejaculation frequency, and the time interval between mare’s parturition and mating.

In this research, from simple analysis, where merely the age of the stallion, sperm volume & concentration, total & progressive motility, and the kinetics (VCL, STR, and LIN) of the sperm were measured. The average volume of sperm was 3.2 ± 0.2 mL, containing 52.6 ± 4.7 × 106 spermatozoa/mL, whereas 30.1 ± 1.7% was motile. And a predictive accuracy of 65.5% is attained, slightly better than 50% without discrimination value.

Meanwhile, the outcome of a cover is successfully predicted with an average accuracy of 94,6% after a detailed analysis (isolated sperm analyzed with specific parameters) from the dismount semen sample of the Thoroughbred horse, and 91.6% per cover with 0.94 AUC values from the ROC analysis. The parameters inspected for the semen analysis that resulted in the high level of predictive accuracy are sperm volume & concentration, total & progressive motility, and complete sperm kinetics reading (VCL, VAP, VSL, STR, and LIN) as seen in Table 1. Where for stallions 1–7, analysis of the dismount sample provided enough information to foresee the result of a given mating with 100, 88.6, 95.2, 100, 78.6, 100, and 100% accuracy, indicating a high level of accuracy for likelihoood of pregnancy prediction.


Table 1 - Quality of the dismount samples for individual stallions

Table 1 - Quality of the dismount samples for individual stallions


In some cases, there might be slightly different factors used to determine the stallion’s fertility and likelihood of pregnancy. For instance, in the case of Stallion 4, the mare’s age was drawn. And for Stallion 5 & 7, the tetrazolium salt reduction ability was included in the regression equation to optimize the analysis.

To recapitulate, the ability of an ejaculate to fertilize and the chances of developing pregnancy after a cover can be predicted after performing an optimized analysis of dismount semen samples from a Thoroughbred horse.

How the iSperm will assist to predict the pregnancy rate?

The iSperm is capable of analyzing the semen sample objectively both for live cover and Artificial Insemination (AI). Check this Link to see how the iSperm performs semen analysis and assist the AI breeding program. The iSperm performs highly accurate prediction of the likelihood of pregnancy from a live cover in this research by reading all of the detailed & important criteria, such as:

  • Concentration (million/mL)
  • Total Motility (%)
  • Progressive Motility (%)
  • Curvilinear velocity (VCL; µm/s)
  • Average path velocity (VAP; µm/s)
  • Straight line velocity (VSL; µm/s)
  • Straightness (STR; VSL/VAP)
  • Linearity (LIN; VSL/VCL)

Furthermore, the sperm kinetics can be adjusted to determine the progressively motile sperm. In this experiment, it’s adjusted to 15 frames acquired at 30 frames/s, slow (static) cell VAP threshold of 20 µm/s, slow (static) cell velocity threshold of 0 µm/s. And cells exhibiting a VAP of >50 µm/s and an STR of >75% were considered progressive. The iSperm can also work with only economical semen volumes, which might be the case with a dismount semen sample.

A mobile computer-assisted sperm analyzer, the iSperm comes in a compact size with a microscope camera and consumable chips that can analyze the semen sample rapidly and accurately both for live cover and AI. Check this Link to see how the iSperm boosts horse's reproductive performance with the AI breeding program.

This article is brought to you by iSperm mCASA, a mobile/mini computer-assisted semen analyzer with high accuracy and affordability for use anytime, anywhere by anyone. Check out www.isperm.co or Contact us to know how helpful iSperm can be for your breeding works.


Citation :

  1. Aitken, R. J., Lambourne, S., & Medica, A. J. (2023). Predicting the outcome of thoroughbred stallion matings on the basis of dismount semen sample analyses. Reproductionhttps://doi.org/10.1530/rep-22-0309
  2. Table 1 - Quality of the dismount samples for individual stallions. Aitken, R. J., Lambourne, S., & Medica, A. J. (2022). Predicting the outcome of thoroughbred stallion matings on the basis of dismount semen sample analyses. Reproduction. Table 2 (p. 286). https://doi.org/10.1530/rep-22-0309
  3. Horse, Gallop, Paddock - free photo on Pixabay. (n.d.). https://pixabay.com/photos/horse-gallop-paddock-galloping-2063672/



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