Post-Thaw Semen Quality Tested

Researchers found non-sperm cells present in fresh semen release an enzyme called MPO during freezing, which could have a negative impact on thawed semen quality.

Photo: Courtesy Lauren M. Gallaspy, DVM

High-quality semen—whether fresh, cooled, or frozen—is a gold standard for successful breeders. So it's not surprising that veterinarians and researchers regularly pour resources into better understanding how to get the best quality semen possible from stallions and into mares. Case in point: Recently, with an eye toward understanding how to produce the most viable semen for artificial insemination, researchers examined the link between non-sperm cells (NSC, epithelial cells or cellular debris present in fresh semen) and myeloperoxidase (MPO, a pro-oxidant enzyme identified in post-thaw semen that is associated with decreased sperm motility).

The researchers subjected semen samples from five actively breeding Quarter Horse stallions to two tests: They either processed the specimens with single-layer colloidal (SLC) centrifugation prior to cryopreservation (cooling to subzero temperatures) or froze them without centrifugation. They measured NSC and MPO concentrations throughout the procedure.

The team's findings showed that the NSC present in fresh semen release MPO during freezing, which could have a negative impact on semen quality. Furthermore, they identified decreased NSC and MPO concentrations in post-thaw semen processed by SLC centrifugation prior to freezing when compared to non-SLC-processed samples.

“This study is aimed at understanding the low quality of post-thaw semen of some stallions,” said Jérôme Ponthier, DVM, MSc., PhD, Dipl. ECAR, at University of Liège’s Clinique Vétérinaire Universitaire in Belgium. “The final aim for the breeders is to increase quality of semen and, thus, pregnancy rate of mares inseminated with frozen semen."

Ponthier said research is underway to further examine the roles of NSC and MPO in fresh and post-thaw semen.

The study, "Effect of non-sperm cells removal with single-layer colloidal centrifugation on myeloperoxidase concentration in post-thaw equine semen," was published in Theriogenology.

About the Author

Natalie DeFee Mendik, MA

Freelance journalist Natalie DeFee Mendik is a multiple American Horse Publications editorial and graphics awards winner specializing in equestrian media. She holds an MA in English from Colorado State University and an International Federation of Journalists' International press card, and is a member of the International Alliance of Equestrian Journalists. With over three decades of horse experience, Natalie’s main equine interests are dressage and vaulting. Having lived and ridden in England, Switzerland, and various parts of the United States, Natalie currently resides in Colorado with her husband and two girls.

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