Equine Study Shows Genetic Abnormalities Cause Infertility

There is more to horse infertility than meets the eye. Advances in cytogenetic analyses using high-tech DNA-based assays have enabled researchers to look at reproductive disorders from a genetic standpoint. After applying the tests to horses with known reproductive issues, a high frequency of sex chromosome abnormalities was identified in horses that are thought to explain both reduced fertility and infertility.

"If genetic anomalies affecting the horse's reproduction efficiency are identified early, breeders can potentially reduce the economic losses caused by open mares, which can be substantial," explained lead author Monika Bugno, PhD, from the National Institute of Animal Production in Balice, Poland.

Bugno and colleagues analyzed the genetic material from 35 horses with a variety of reproductive disorders, including lack of progeny, subfertility, irregular estrous cycles, infertility, poor semen parameters, and lack of--or suppression of--libido.

Only 21 horses (60%) had normal karyotypes (i.e., all 64 chromosomes and the correct sex chromosomes, either XX or XY).

"Of the chromosome abnormalities identified in the remaining 14 horses, the most common abnormalities involved the X chromosome," reported Bugno. That is, many mares had too many or too few X chromosomes.

"At present, these molecular techniques are prohibitively expensive and can not be used to analyze all of a horse's chromosomes to identify abnormalities that could impact their reproductive performance," said Bugno.

This technology is not available for commercial use, but if a detailed analysis of a specific horse's DNA is needed, blood samples could be sent to Dr. Bugno at the Institute.

Bugno and colleagues are also using molecular probes to analyze stallions' sperm for abnormalities in sex chromosomes (aneuploidy of heterosomes).

The study, "Identification of chromosome abnormalities in the horse using a panel of chromosome-specific painting probes generated by microdissection" will be published in the September 2009 edition of the journal Acta Veterinaria Hungarica. The abstract is currently available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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