Sperm Kinematic Differences Between Cloned and Non-Cloned Polo Argentino Stallions

Sperm Kinematic Differences Between Cloned and Non-Cloned - sperm cell on black backgroundCloned horses produced via somatic cell nuclear transfer do not retain the mitochondrial DNA of the founder animal, as mitochondria are derived from the recipient oocyte. Given the established role of mitochondria in sperm motility and energy production, this first-of-its-kind study compared sperm kinematic profiles between cloned and non-cloned Polo Argentino stallions under commercial field conditions.

Study Design:

  • 53 Polo Argentino stallions from 7 embryo transfer centers; ages 4–10 years
  • Non-cloned stallions with original mitochondria (n=45) vs. cloned stallions with somatic cell nuclear transfer-replaced mitochondria (n=9)
  • Semen collected, filtered, and diluted; computer-assisted sperm analysis performed at 5 minutes, 60 minutes, and 120 minutes of incubation at 37°C
  • Eight kinematic parameters measured alongside total and progressive motility and velocity subpopulations

Key Results:

  • No significant differences in total or progressive motility between groups at any timepoint
  • Non-cloned stallions consistently showed superior average path velocity, curvilinear velocity, and amplitude of lateral head displacement (p<0.001)
  • Cloned stallions showed higher straightness values (p<0.05) — indicating less lateral head movement
  • Non-cloned stallions had a higher percentage of intermediate and fast spermatozoa (p<0.001); differences most pronounced at 120 minutes

Conclusions:

  • Cloning via somatic cell nuclear transfer produces measurable differences in sperm kinematics despite equivalent gross motility
  • Findings implicate mitochondrial genome origin as a potential contributor to sperm movement dynamics
  • First study to assess sperm dynamics in cloned horses; larger studies are warranted

(Aranda Lopez L, LaBanca M, Molina A, Demyda-Peyrás S. 2025. Sperm characterization of cloned and non-cloned horses: preliminary results reveal differences in kinematic patterns. Journal of Equine Veterinary Science 145:105263. https://doi.org/10.1016/j.jevs.2024.105263)