Veterinary andrology studies male reproduction, including testicular physiology, endocrinology, spermatogenesis, sexual behavior, semen evaluation, reproductive tract disorders, and applied biotechnologies. Understanding these processes is essential to improve fertility, reproductive efficiency, and productive performance. (Senger, 2020)
1. Testicular Physiology and Endocrine Function
The testes perform two key functions: sperm production and hormone secretion. Spermatogenesis occurs in the seminiferous epithelium under strictly regulated conditions: temperature 2–6°C lower than body temperature, adequate blood flow, Sertoli cell integrity, and hormonal stimulation. Endocrinologically, testosterone maintains libido, muscle development, reproductive behavior, and sexual differentiation. (Hafez & Hafez, 2016)
- GnRH: stimulates pulsatile release of LH and FSH.
- LH: acts on Leydig cells → testosterone production.
- FSH: stimulates Sertoli cells and supports spermatogenesis.
- Testosterone: regulates sexual behavior and spermiation.
- Dihydrotestosterone (DHT): important for accessory glands.
- Inhibin: negative feedback on FSH.
Endocrine disruption due to stress, toxins, or inflammation severely impacts fertility. (Senger, 2020)
- Optimal testicular temperature (thermoregulation via dartos, cremaster, and pampiniform plexus).
- Adequate nutrition (energy, antioxidants, zinc, selenium).
- Photoperiod (especially important in sheep and goats).
- Age and sexual maturity.
Young males show a higher incidence of transient alterations in semen quality.
2. Spermatogenesis and Maturation
Spermatogenesis is a continuous process divided into mitotic, meiotic, and differentiation phases. Each stage depends on the integrity of the seminiferous epithelium and the hormonal microenvironment. After formation, spermatozoa pass into the epididymis to acquire progressive motility, membrane stability, and fertilizing capacity. (Hafez & Hafez, 2016)
- Spermatogonial phase: cellular proliferation.
- Spermatocytic phase: meiosis and genetic recombination.
- Spermatid phase: structural differentiation.
- Epididymal maturation: motility, condensation, and membrane stability.
Trauma, fever, heat stress, or toxins affect spermatogenesis for 45–60 days afterward.
3. Semen Evaluation
Semen analysis is the diagnostic cornerstone for assessing male fertility. Besides basic parameters, modern evaluation includes functional, biochemical, and advanced tests (CASA, ROS measurement, acrosomal integrity). (Barth, 2018)
- Volume, odor, and color.
- Sperm concentration.
- Mass, progressive, and individual motility.
- Morphology: primary, secondary, and tertiary defects.
- Membrane integrity: HOST, eosin-nigrosin.
- Vitality: supravital stains.
- Acrosomal integrity: PSA-FITC, enzymatic tests.
A single semen test cannot diagnose infertility; 2–3 evaluations are recommended.
- CASA: computer-assisted motility analysis.
- Flow cytometry: DNA and membrane integrity.
- Reactive oxygen species detection: oxidative stress.
- Thermal assays: semen cold resistance.
These tools better predict real fertility in field conditions.
4. Common Andrological Disorders
Failure of testicular descent, common in dogs and horses. The retained testis undergoes degeneration and carries an increased tumor risk. It drastically reduces semen quality and is hereditary.
Inflammation caused by bacterial, viral, or traumatic agents. In cattle, Brucella abortus is highly relevant. These conditions cause pain, fever, testicular degeneration, and azoospermia.
Caused by hormonal disorders, systemic disease, heat stress, or degenerative processes. It affects testosterone production, libido, and sperm output.
Including decreased libido, incomplete ejaculation, mounting problems, or refusal of the female. They may be related to pain, poor training, environmental factors, or low testosterone.
5. Assisted Reproductive Techniques
Reproductive biotechnologies improve genetic dissemination, preserve valuable genetic material, and optimize fertility. They require high-quality semen and proper handling.
- Artificial insemination (AI) with fresh, chilled, or frozen semen.
- Cryopreservation and germplasm banks.
- Collection using artificial vagina or electroejaculation.
- Post-thaw evaluation and cold tolerance tests.
- Sperm selection via gradients or microfluidics.
Semen quality determines the success of all reproductive biotechnologies.
Conclusion
Veterinary andrology is essential for diagnosing infertility, implementing reproductive management, and improving genetics. Understanding testicular physiology, hormonal interactions, spermatogenesis, and common disorders allows optimizing reproductive efficiency in both productive and clinical settings. Advanced semen evaluation techniques increase diagnostic precision and enhance reproductive decision-making. (Senger, 2020)
References
• Senger, P.L. (2020). Pathways to Pregnancy and Parturition.
• Hafez & Hafez. (2016). Reproduction in Farm Animals.
• Barth, A. (2018). Bovine Andrology.