The Effects of Aging and Cryopreservation on Canine Semen Quality
While artificial insemination (AI) is commonly used in canine breeding, there is still much to learn about which sperm characteristics accurately predict fertility following AI. Thanks to AKC Canine Health Foundation (CHF) funding, Dr. Stuart Meyers and his team at the University of California, Davis - including American Kennel Club/Theriogenology Foundation theriogenology resident Dr. Andrea Hesser - explored the effects of age and sperm characteristics on fertility. With funding from CHF Grants 02124-A and 02192-A, they studied a population of Labrador Retriever stud dogs from the nonprofit organization Guide Dogs for the Blind, for which semen characteristics and fertility were recorded over several years. This type of research may help veterinarians and breeders more accurately predict the fertility of an individual stud dog.
Data showed that differences in the quality of fresh and extended chilled semen (as determined by the standard parameters of motility, morphology, and concentration) ultimately had no effect on fertility or fecundity, regardless of the stud dog’s age.1 The research team then explored the effects of dog age on fresh and frozen semen. They also evaluated samples from client-owned, sub-fertile dogs (as defined by the referring veterinarian) to compare thawed semen quality among dogs with varied fertility histories. These results were recently accepted for publication in the journal Theriogenology,2 and showed that average path velocity was the only sperm characteristic of fresh semen that demonstrated a statistically significant decline with age. All sperm qualities measured were lower in frozen sperm compared to fresh sperm, but reductions in total motility, progressive motility, and average path velocity were exaggerated in older dogs. Results also substantiated that the viability of thawed frozen sperm from fertile dogs is much higher than that of sub-fertile dogs. This could indicate that cryopreservation has a bigger impact on sub-fertile dogs, but the lack of pre-freeze semen evaluation in the sub-fertile dogs studied means that cryopreservation itself may not be the sole cause of the observed difference.
Overall, this research demonstrates that freezing does decrease sperm quality and that sperm motility seems to be a sensitive indicator of cell damage from the freeze-thaw process. The damaging effects of cryopreservation become more pronounced as a dog ages. Practically, this emphasizes that it is better to freeze semen when a dog is young. Cryopreservation of canine semen facilitates easy transport, a diverse gene pool, and control of infectious diseases. A better understanding of the relationships between freezing, dog age, and dog fertility will improve the handling, transportation, and predictability of this valuable resource. Stay up to date with CHF-funded research on reproductive conditions and more at akcchf.org/research.
1. Hesser, A., Darr, C., Gonzales, K., Power, H., Scanlan, T., Thompson, J., … Meyers, S. (2017). Semen evaluation and fertility assessment in a purebred dog breeding facility. Theriogenology, 87, 115–123.
2. Fuente-Lara Adl, Hesser A, Christensen B, Gonzales K, Meyers S. (2019). Effects from aging on semen quality of fresh and cryopreserved semen in Labrador Retrievers, Theriogenology.
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