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Frozen Semen Overview

Semen quality must be good for freezing.

  • 150 million minimum needed 
  •  Average for  Large dogs (25-45kg) : 600-800 million sperm cells/ejaculate
  • Collection impacts count- miss some, dog not aroused


  • 70% forward motility minimum needed
  •  Average for  Large dogs (25-45kg) : 600-800 million sperm cells/ejaculate
  •  Environment impacts motility- temperature, assess immediately or keep at proper temp
  • 1-2 hrs -room temperature (20-22°C),  >  dilute in extender, cool slowly to 4-5° C)


  • > 70% normal morphology considered normal- higher the better but always some
  • >30% abnormal- Don’t freeze
  • >50% abnormal- Risk of infertility


  • Ejaculate male 2 days prior to analysis if hasn’t been ejaculated recently, 
  • >12 months old best or may have abnormalities due to sexual immaturity

Main Sperm Defects in Dogs






Spermatogenesis Abnormalities

Macrocephalus, microcephalus, double, pointed, indented heads

Thickened, eccentric insertion

Thickened (swollen, thinned, coiled, kinked, double midpiece

Thin, double, triple tail

Maturation, ejaculation or handling

Free, bent heads, swollen acrosomes, detaching acrosomes

Bent midpiece, extraneous material surrounding midpiece, proximal, mid and distal cytoplasmatic droplets

Coiled, looped, kinked, folded, detached tail.

Chart:  Artificial Insemination in Dogs, Rita Payan-Carreira1, Sónia Miranda2 and Wojciech Niżański, Poland

Images from Colorado State and http://therio.vetmed.lsu.edu/sperm_abnormal_print.htm, fertilitypedia.org

Which defects matter with frozen semen?

  • Proximal droplets: Don’t freeze, Maturation defect that impacts fertility
  • Any defect that impairs movement, viability
  • Primary Head Defects – impacts DNA. May penetrate egg but no pups result
  •  Not all abnormalities impact fertility – But they may impact viability of frozen semen
  •  You can’t see all abnormalities

Clinical and Structural Features of Sperm Head Vacuoles in Men Included in the In Vitro Fertilization Programme

Nina Fekonja,1 Jasna Štrus,1 Magda Tušek Žnidarič,1,2 Katja Knez,2 Eda Vrtacnik Bokal,3 Ivan Verdenik,3 and Irma Virant-Klun3

Frozen Semen Handling - Potential points of failure

  • Collection- contaminants (blood, chemicals)
  • Extender used
  • Chilling procedure to prepare for freeze
  • Freeze temperature and  speed
  • Storage – always in LN2
  • Thaw temperature

Additional Resources

  • Sperm Motility – Principles – Melissa Rouge, Colorado State University – http://www.vivo.colostate.edu/hbooks/pathphys/reprod/semeneval/motility.html

Additional References

  1. Charlesworth, D., Willis, J. The genetics of inbreeding depression. Nat Rev Genet 10, 783–796 (2009). https://doi.org/10.1038/nrg2664