Breeding Soundness Evaluation in Dogs: A Practical Clinical Framework for Veterinary Practitioners

Reproductive efficiency in dogs is not just a biological concern; it has emotional and financial implications for breeders and pet owners alike. Healthy genital function and optimal semen quality are fundamental prerequisites for successful breeding outcomes. Any impairment in fertility may lead to reduced litter sizes or complete failure of conception, resulting in significant disappointment and economic losses¹. In this context, Breeding Soundness Evaluation (BSE) becomes an indispensable diagnostic and screening tool for veterinarians working with breeding animals. 

Understanding the Scope of Breeding Soundness Evaluation 

A comprehensive BSE aims to assess the reproductive health and breeding potential of a male dog. It includes a combination of andrological examination, hormonal profiling, and semen analysis^1,2. However, beyond theoretical knowledge, the real clinical value lies in accurate execution and interpretation, especially in cases involving semen preservation, artificial insemination, or suspected infertility¹. 

The process begins with a detailed anamnesis, which is often underestimated in practice. Clinicians must collect thorough reproductive history, previous mating outcomes, medication exposure, and even geographical movement of the animal, as these factors can influence reproductive health¹. 

Morphological and Hormonal Assessment: Clinical Insights 

The morphological examination focuses on evaluating the size, symmetry, consistency, and position of reproductive organs. These parameters provide initial clues about normal or pathological conditions. For instance, small and soft testicles may indicate low testosterone levels, which can also affect prostate function¹. 

Hormonal evaluation further enhances diagnostic precision. The hypothalamic-pituitary-gonadal axis plays a central role in regulating reproduction. Gonadotropin-releasing hormone (GnRH) stimulates the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which in turn regulate testosterone production and spermatogenesis. However, clinicians must be cautious while interpreting hormone levels, especially testosterone, as natural fluctuations can reach up to 62%, necessitating repeated sampling in some cases¹. 

The GnRH stimulation test is particularly useful in evaluating testicular function and confirming the presence of testicular tissue. Additionally, biomarkers such as canine prostate-specific esterase (CPSE) have emerged as potential tools for early detection of prostatic diseases, although variability in cutoff values limits their standalone diagnostic reliability^1,3. 

Role of Imaging and Advanced Diagnostics 

Ultrasound remains a cornerstone for evaluating reproductive organs, particularly the prostate. Changes in echogenicity and glandular structure can indicate pathology, although they are not disease-specific. Advanced Doppler parameters such as resistance index (RI) and pulsatility index (PI) have been explored, but their predictive value for fertility remains inconclusive^1,4. 

Despite technological advancements, a significant gap exists in the standardization and validation of these tools, emphasizing the need for cautious interpretation and integration with clinical findings¹. 

Timing and Practical Considerations in BSE 

The timing of evaluation plays a crucial role in obtaining reliable results. Spermatogenesis in dogs takes approximately 56–63 days, making it essential to review medical history for at least six months prior to evaluation¹. Recent semen collection, prolonged sexual rest, and even seasonal variations can influence semen quality^1,5,6. 

Clinically, it is important to standardize conditions as much as possible. For instance, prolonged abstinence may increase morphologically abnormal sperm, while frequent collection may reduce sperm concentration¹. 

Semen Analysis: Beyond Basic Parameters 

Semen analysis remains a central component of BSE, focusing on sperm concentration, motility, and morphology. These parameters provide valuable insights but must be interpreted in context. For example, body weight significantly influences semen characteristics, suggesting the need for size-adjusted reference values¹. 

Advanced techniques such as computer-assisted sperm analysis (CASA) and flow cytometry offer more precise evaluation, but their availability in routine practice is limited. Additionally, tests like hypoosmotic swelling and alkaline phosphatase measurement can provide supplementary information¹. 

Clinical Challenges and Interpretation 

One of the biggest challenges in veterinary andrology is the limited predictive value of semen parameters. Even dogs with suboptimal semen quality may achieve conception, while those with apparently normal parameters may fail. This uncertainty highlights the importance of a multiparametric approach and repeated evaluations when necessary¹. 

Moreover, external factors such as collection technique, stress, and environmental conditions can significantly affect results, underscoring the need for strict quality control and standardized protocols¹. 

Conclusion: Integrating Science with Clinical Judgment 

Breeding Soundness Evaluation is a powerful tool, but its effectiveness depends on the clinician’s ability to integrate multiple diagnostic findings with practical experience. While current methods provide valuable insights, they are not absolute predictors of fertility. 

For veterinary practitioners, the key lies in holistic assessment, repeated evaluations, and clear communication with breeders regarding the limitations of diagnostic tools. As emerging technologies and biomarkers continue to evolve, the future of canine reproductive diagnostics holds promise, but clinical judgment will remain irreplaceable. 

References: 

1. Arlt SP, Reichler IM, Herbel J, Schäfer-Somi S, Riege L, Leber J, Frehner B. Diagnostic tests in canine andrology-What do they really tell us about fertility?. Theriogenology. 2023 Jan 15;196:150-6. https://doi.org/10.1016/j.theriogenology.2022.11.008 

2. de Souza MB, England GC, Mota Filho AC, Ackermann CL, Sousa CV, de Carvalho GG, Silva HV, Pinto JN, Linhares JC, Oba E, da Silva LD. Semen quality, testicular B-mode and Doppler ultrasound, and serum testosterone concentrations in dogs with established infertility. Theriogenology. 2015 Sep 15;84(5):805-10.  https://repositorio.unesp.br/bitstreams/9ac434cd-60a9-437b-9314-af7523235cd2/download 

3. Holst BS, Holmroos E, Friling L, Hanås S, Langborg LM, Franko MA, Hansson K. The association between the serum concentration of canine prostate specific esterase (CPSE) and the size of the canine prostate. Theriogenology. 2017 Apr 15;93:33-9. https://www.academia.edu/download/111910909/j.theriogenology.2017.01.03220240228-1-q92im.pdf 

4. England GC, Bright L, Pritchard B, Bowen IM, De Souza MB, Silva LD, Moxon R. Canine reproductive ultrasound examination for predicting future sperm quality. Reproduction in Domestic Animals. 2017 Apr;52:202-7. https://www.researchgate.net/profile/Lucia-Silva-12/publication/309684658_Canine_reproductive_ultrasound_examination_for_predicting_future_sperm_quality/links/5b51f6e7aca27217ffa7d080/Canine-reproductive-ultrasound-examination-for-predicting-future-sperm-quality.pdf 

5. Lechner D, Aurich J, Schäfer-Somi S, Aurich C. Effects of age, size and season on cryotolerance of dog semen–A retrospective analysis. Animal reproduction science. 2022 Jan 1;236:106912. https://www.sciencedirect.com/science/article/pii/S037843202100227X 
6. Lechner D, Aurich J, Schäfer‐Somi S, Herbel J, Aurich C. Combined cryopreservation of canine ejaculates collected at a one‐hour interval increases semen doses for artificial insemination without negative effects on post‐thaw sperm characteristics. Reproduction in Domestic Animals. 2021 Sep;56(9):1220-6. https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/rda.13980