02124-A: Determining the Characteristics of Sperm That Accurately Predict Fertility of Stud Dogs
Grant Status: Closed
Measures of semen quality in stud dogs have not been subjected to a longitudinal study that includes endpoints of female fertility and pregnancy. Consequently, components of semen that affect female fertility have not been sufficiently identified in breeding dogs. With the growing use of artificial insemination (AI) and the use of frozen semen in dog breeding evident, we quite simply do not know the level of predictability and odds of fertile matings for any breed of dogs. This research will, for the first time, allow semen evaluation in a large population of a single breed of valuable service dogs (Labrador Retrievers) in which semen characteristics and known fertility has been tracked for a number of years. We evaluated 39 Labrador Retriever males at stud at Guide Dogs for the Blind (GDB), San Rafael, California from October, 2014-February, 2015. We obtained two ejaculates on separate occasions from each dog by manual collection using an estrus female as mount. We determined the sperm endpoints in fresh semen and extended chilled semen at 24hrs post-collection, and we cryopreserved semen in polyethylene straws for future evaluation, the latter of which is currently in progress in our laboratory. Sperm endpoints evaluated were total and progressive motility, average path velocity (VAP), morphology, lipid oxidation status, presence of oxygen free radicals (reactive oxygen species, ROS), sperm chromatin structure (SCSA), and mitochondrial DNA copy numbers and DNA deletions. Fresh semen data were analyzed by individual dog and by age group. Dogs varied in age from 1 to 10 years, and were subdivided into young (1 to 3 years, n=21), middle-aged (4 to 6 years, n=13), and senior (7 years or greater, n=5) for comparison. Overall, there were no differences in semen parameters between males (p>0.01). However, when dogs were grouped by age, there were observed differences (p<0.01) in sperm quality by age in percentage of morphologically normal sperm and average path velocity (VAP). Dogs more than 7 years of age tended to have lower and more variable percentages of normal sperm in their ejaculates and displayed lower sperm velocity when compared to dogs younger than 6 years of age. We evaluated the likelihood of differences in pregnancy rate and litter size in females mated to dogs of different ages, and whether these fertility endpoints were responsive to variation in semen quality. As expected for this normal healthy and highly fertile stud population, we observed no effects from semen quality on fertility or fecundity, although several seminal parameters differed with age. These data will provide Theriogenologists a normal semen database for Labrador Retrievers, the largest breed in the US. The approach allows veterinarians a look at traditional measures and newer non-traditional measures of semen quality and begin to objectively question the validity of semen analysis. To our knowledge, this study is the first to evaluate semen and fertility parameters as they relate to canine age. The use of advanced laboratory tests to evaluate sperm parameters beyond the classic motility, morphology, and concentration may open the door to more specific and sensitive fertility tests in canine reproduction.
Manuscript in preparation.
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