Sperm parameters in the Great Dane: Influence of age on semen quality.

Not all sires have sperm suitable for chilled or frozen storage, and success in artificial insemination (AI) varies highly among individual dogs and breeds. Fertilizing potential is further complicated as sperm quality declines with the aging process. Due to the rapidity of aging and senescence in large breed dogs, associated health and fertility changes may be observed over a shorter period, though this period remains undefined for any breed. Working with a population of purebred Great Danes (GD), our aims were (1) to characterize the distribution of a series of sperm parameters, (2) to distinguish sources of variation in sperm quality within this rapidly aging breed, and (3) to identify changes in sperm quality that may accompany aging. Ejaculates collected from young, middle-aged, and senior Great Dane dogs (n = 50) were evaluated for semen volume, total sperm number and viability, and reactive oxygen species (ROS), in addition to sperm morphology and kinematic parameters. Total testicular volume was also determined using ultrasonography. Testicular volume was not a predictor of sperm production in the GD, however, significant differences between coat colors were identified. Age was negatively associated with total motility, progressive motility, and amplitude of lateral head displacement (ALH) (p < .05). We identified significant relationships between GD male age and TM, PM, and immotility with -9.9%, -9.0%, and +8.3% change per year of age, respectively, which support the anecdotal reports of decline of the fertility with the advance of age in this breed. Sperm of younger GD dogs aged 12 ≤ x < 24 months had significantly higher TM, PM, ALH, and nonlinear motility (p < .05) than older dogs (x ≥ 48 months). High ROS levels were positively associated with TM and PM, average pathway distance (DAP) and straight line distance (DSL), average pathway velocity (VAP), straight line velocity (VSL), and the presence of hairpin tails (p < .05). While age and ROS have significant influences on sperm parameters in the GD, the influence of selection for breed specific phenotypes could help explain the functional significance of the diversity among GD males.

Effects from aging on semen quality of fresh and cryopreserved semen in Labrador Retrievers.

Characteristics of frozen sperm associated with fertility and aging have not been fully determined in dogs. The aim of this study was to determine the relationship between fresh and post-thaw sperm quality, age, among the factors of motility, viability, morphology and oxidative stress in a group of fertile stud dogs with extensive breeding records and in dogs with reported subfertility problems. Sperm parameters from 39 fertile dogs were measured in fresh semen and frozen thawed semen. Additionally, frozen semen from 9 subfertile dogs was thawed and analyzed. Subfertile dogs were defined by referring veterinarians solely on the basis of owner history; breeding records were not available to this study. Evaluation included total motility (TM) and progressive motility (PM), average path velocity (VAP), viability, morphology and presence of sperm reactive oxygen species (ROS). Fertile males' ages ranged from 1 to 10 years, subfertile males' ages ranged from 4 to 14 years. All dogs were assigned to age groups according to age as young (1-3 years) middle (4-6 years) and senior (>7 years). The effect of sperm state (fresh vs. frozen-thawed), age, and fertility history (fertile vs. subfertile) on the measured endpoints were determined using a mixed effects model. TM showed a negative correlation with age in the frozen-thawed semen. Additionally, TM in fresh semen was higher in all age groups compared to post thaw semen (P < 0.05). PM was higher in all age dogs of fresh semen compared to frozen-thawed semen (P < 0.05). As such, TM and PM in post thaw semen statistically decreased compared to fresh semen regardless of age of stud male (P < 0.05). Differences in VAP were only observed between young and senior age groups in fresh semen (P < 0.05) while young and middle age dogs from fresh semen were different in all age groups for frozen-thawed semen (P < 0.05). ROS was higher in the young frozen-thawed semen compared to the young fresh semen (P < 0.05). When comparing TM, PM and VAP of fertile vs. subfertile dogs, middle aged fertile dogs are different from middle aged and senior subfertile dogs (P < 0.05). No differences were found in measures of ROS between fertile and subfertile. For sperm viability and morphology, differences were observed between all age groups of fertile dogs in comparison to all ages of subfertile dogs (P < 0.05). Sperm motility appeared to be the most affected parameter by freezing damage than any other parameter measured in this study, while we were not able to determine a significant association between ROS production and fertility status.

Semen evaluation and fertility assessment in a purebred dog breeding facility.

Semen quality in dogs has not been assessed in a longitudinal study that includes endpoints of female fertility and pregnancy. Although use of artificial insemination with chilled semen is increasingly used in canine reproduction, the resultant level of predictability and odds of fertile matings for dogs is still not fully understood. This research provides, for the first time, comprehensive semen evaluation in a large population of dogs in which fertility has been tracked. Duplicate ejaculates were obtained from 39 Labrador retriever males of the Guide Dogs for the Blind (San Rafael, CA, USA) breeding program. Sperm endpoints were determined in fresh semen and extended chilled semen at 48 hour after collection. Evaluation included total and progressive motility, average path velocity, morphology, membrane lipid peroxidation, presence of sperm reactive oxygen species, sperm chromatin structure, and mitochondrial DNA copy number. Male age ranged from 1 to 10 years and were grouped as young (Y; 1-3 years, n = 21), middle aged (M; 4-6 years, n = 13), and senior (S; 7 years or greater, n = 5) for analysis. The effects of age and sperm state (fresh vs. chilled) on the above sperm endpoints were determined using a linear mixed effects model. Semen endpoint values for all parameters were established for this group of fertile males. Progressive motility was only lower in the senior male chilled samples compared to all other groups, fresh and chilled (P < 0.05). Velocity decreased with increasing age and was lower overall in chilled samples (P < 0.05). Percent morphologically normal sperm was lower in senior dogs compared with the other age groups (P < 0.05). The presence of reactive oxygen species was lower in chilled samples compared with fresh (P < 0.05). For sperm chromatin structure, the senior-aged group had a higher %COMPαt than the middle-aged group (P < 0.05). Bayesian analysis determined that no differences were seen in total motility, membrane lipid peroxidation, and mitochondrial DNA copy number, with regard to conception rate or average litter size between age groups or between fresh and chilled samples. We observed no effects from semen quality on fertility or fecundity regardless of age, despite the differences found in semen quality. The use of advanced laboratory tests to evaluate sperm parameters beyond the standard motility, morphology, and concentration will open investigation to more specific and sensitive fertility tests in canine reproduction.

Spermatocele in a South African Boerboel dog.

A 2-year-old intact male South African Boerboel presented for semen cryopreservation and was discovered to be azoospermic. The dog had excellent libido and had sired litters within 6 months, so a further investigation of why his collection lacked sperm was warranted. On further examination of his scrotal contents, his right epididymis had an enlarged area with a hard texture. Ultrasonography revealed that the enlarged area of the right epididymis was fluid filled. A sample of the fluid was aspirated for aerobic culture. No bacteria showed growth. Although the culture was negative, it was suspected that this dog had an epididymitis or epididymal abscess, and treatment with enrofloxacin at 10mg/kg orally was initiated for 4 weeks. The abnormal texture and fluid-filled cavity in the right epididymis persisted, despite antibiotic therapy. Cytology of a repeat aspiration of the fluid-filled area after antibiotic therapy revealed a mixture of red blood cells and sperm. Owing to the potential for blood-testis barrier disruption, a unilateral orchiectomy of the right testicle was performed, as an attempt to protect future sperm production of the remaining testicle. A spermatocele was confirmed on histopathology. After another month, an excellent-quality semen sample was collected, with 90% progressive motility, good concentration, and few morphologic abnormalities. A subsequent collection was acquired and was successfully cryopreserved for future breeding. In dogs with spermatoceles, semen quality can be preserved with aggressive treatment to remove the affected testicle. The disruption of the blood-testis barrier in spermatoceles may result in antisperm antibody production and eventual infertility; however, cryopreservation can result in long-term options for owners seeking to continue using an animal in their breeding program.