Artificial insemination (AI) is a common practice in canine reproduction, and in addition to the practice of AI, the use of chilled or frozen sperm has increased in popularity. But what are the effects of these storage methods on reproductive outcomes? Routine analysis of semen typically looks at morphology, motility, and velocity of the sperm, as well as the overall count of sperm present. Using this common analysis of sperm, little is known about how these qualities are linked to actual fertility rates in stud dogs. Correlating characteristics of sperm to fertility rates, as well as identifying new determinants of quality semen, is important to improve the level of predictability for successful mating.
In 2014, Dr. Stuart Meyers and his team at the University of California, Davis received a grant from the AKC Canine Health Foundation (CHF) to further his work in this area. The grant (02124-A) was entitled “Determining the Characteristics of Sperm That Accurately Predict Fertility of Stud Dogs.” Dr. Meyers’ team set out to look at sperm characteristics as they relate to pregnancy outcome in Labrador Retrievers. The researchers tracked the quality of sperm specimens from stud dogs at the Guide Dogs for the Blind breeding program. This marked the first comprehensive study of sperm parameters and male fertility in a group of highly fertile stud dogs of a single breed.
In addition to routine semen quality measures, advanced measures including lipid peroxidation, oxidative metabolism, sperm chromatin structure assay (SCSA), mitochondrial DNA, and reactive oxygen species (ROS) were also performed. Analysis was performed on samples that were collected and then later analyzed after being either chilled or frozen. The sample population was separated by age to begin to explore the role that aging might have on the quality of semen used for AI. Not only did this study aim to improve the overall knowledge of the relationship between sperm quality and fertility outcomes, it also presented a unique opportunity for training in the field of theriogenology (a branch of veterinary medicine concerned with veterinary obstetrics and with the diseases and physiology of animal reproductive systems).
One of the first American Kennel Club (AKC)-funded AKC/Theriogenology Foundation theriogenology residents, Dr. Andrea Hesser, was involved in this research project and was first author on a 2017 publication resulting from these studies. Drs. Meyers, Hesser, and colleagues found that in the older fertile dogs, some semen parameters changed with age and state (fresh or chilled), including decreased percent normal morphology and average path velocity (VAP), despite the dog maintaining a high fertility rate. The magnitude of this change was very small relative to what might be expected from dogs with significant fertility problems.
To further enhance the impact of these findings, Dr. Meyers received a second CHF-funded grant (02192-A), entitled “Advanced Semen Analysis in Labrador Retrievers.” In this study, the investigators compared the database of sperm characteristics in highly fertile stud dogs to dogs that were either sub-fertile or infertile. With a better understanding of the effects storage has on semen samples, it was possible to analyze more samples from sub-fertile dogs to determine what other factors affect the overall quality of the semen. From the population of sub-fertile dogs, the semen had lower sperm motility, normal sperm morphology, and viability. It was also determined that there was increased production of reactive oxygen species (ROS), indicating lower sperm quality, in general. Dr. Meyers presented some of the results from this study at the 2017 AKC Canine Health Foundation National Parent Club Canine Health Conference in St. Louis. These findings have potential implications for the establishment of characteristics that affect pregnancy outcomes and the use of advanced semen analyses in canine reproduction.