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)