Canine infertility is defined as the inability to conceive and deliver viable puppies despite proper breeding management.
Overview and Clinical Importance
Canine infertility is defined as the inability to conceive and deliver viable puppies despite proper breeding management. This is a frequently tested topic on the NAVLE, requiring understanding of both female (bitch) and male (stud dog) reproductive physiology, proper breeding timing, and common causes of reproductive failure. The most critical concept: improper breeding management is the most common cause of apparent infertility in dogs.
Infertility evaluation requires a systematic approach, categorizing patients as either cyclic (regular estrous cycles) or acyclic (absent/irregular cycles), then investigating specific causes. This guide covers diagnostic approaches, etiologies, and treatments for both sexes.
| Phase |
Duration |
Hormonal Changes |
Clinical Signs |
| Proestrus |
3-21 days (avg 9) |
Rising estrogen, low progesterone |
Vulvar swelling, bloody discharge, attracts males but refuses breeding |
| Estrus |
3-21 days (avg 9) |
Declining estrogen, rising progesterone, LH surge |
Receptive (standing, flagging), straw-colored discharge |
| Diestrus |
56-58 days (pregnant) or 60-100 days |
High progesterone (CL function) |
Refuses breeding, pregnancy or pseudopregnancy |
| Anestrus |
1-6 months |
Low estrogen and progesterone |
Reproductive quiescence |
Canine Estrous Cycle Review
The bitch is monoestrous and non-seasonal in most breeds, with an average interestrous interval of 5-8 months.
Estrous Cycle Phases
NAVLE TipRemember "P.E.D.A." for cycle phases: Proestrus, Estrus, Diestrus, Anestrus. LH surge at proestrus-estrus transition; ovulation 24-72 hours after LH surge.
| Progesterone Level |
Reproductive Event |
Clinical Action |
| Less than 1 ng/mL |
Baseline (proestrus) |
Monitor every 2-3 days |
| 2-3 ng/mL |
LH surge (Day 0) |
Begin daily monitoring |
| 4-10 ng/mL |
Ovulation (Day 2) |
Breed in 2-4 days |
| 15-25+ ng/mL |
Optimal fertile period (Days 4-6) |
Optimal breeding window |
Ovulation Timing and Breeding Management
Proper ovulation timing is the single most important factor in successful breeding. Unique canine features:
- Bitches ovulate primary oocytes requiring 48-72 hours to mature
- Ovulation occurs with rising progesterone (4-10 ng/mL)
- Optimal breeding: 2-4 days AFTER ovulation
- Fresh semen survives 5-7 days in female tract
Progesterone Values for Breeding Timing
Vaginal Cytology Interpretation
High-YieldCell shapes: Parabasal = "O" (doughnut), Intermediate = "Fried Egg", Superficial = "Corn Flake" (angular). Greater than 80% superficial = cytologic estrus.
| Stage |
Cell Type |
Other Findings |
Significance |
| Anestrus |
Parabasal and small intermediate |
Low cellularity |
Reproductive quiescence |
| Early Proestrus |
Intermediate (less than 50% superficial) |
RBCs, neutrophils |
Begin progesterone monitoring |
| Estrus |
Superficial (greater than 80%) |
Clear background, bacteria, no neutrophils |
Fertile period |
| Diestrus |
Return of intermediate/parabasal |
Abundant neutrophils |
Fertile period ENDED |
Female Infertility (Bitch)
Female infertility is categorized into: cyclic bitches (normal cycles, failing to conceive) and acyclic bitches (absent/abnormal cycles).
Causes of Infertility in the Cyclic Bitch
| Category |
Specific Causes |
Diagnostic Approach |
| Breeding Management (MOST COMMON) |
Improper timing, inadequate frequency, male subfertility |
Serial progesterone, vaginal cytology, semen evaluation |
| Uterine Disorders |
CEH, endometritis, mucometra, congenital anomalies |
Ultrasound, uterine culture, biopsy |
| Infectious |
Brucella canis (ALWAYS rule out), CHV, Mycoplasma |
Brucella serology, PCR, culture |
| Hormonal |
Hypoluteoidism, hypothyroidism (uncommon) |
Serial progesterone, thyroid panel |
Cystic Endometrial Hyperplasia-Pyometra Complex
Cystic endometrial hyperplasia (CEH) is a progressive, progesterone-mediated uterine pathology predisposing to bacterial infection (pyometra). Major cause of infertility and can be life-threatening.
Pathophysiology
- Repeated estrogen/progesterone cycles cause endometrial glandular proliferation
- Progesterone suppresses local immunity and closes cervix during diestrus
- Ascending vaginal bacteria (primarily E. coli) colonize abnormal endometrium
- Open pyometra: vaginal discharge. Closed pyometra: no discharge, more severe illness
Clinical Signs and Diagnosis
Treatment Options
NAVLE TipPyometra = middle-aged intact bitch, 1-2 months post-estrus, PU/PD, lethargy, vaginal discharge (if open). Treatment of choice = OHE after stabilization. Medical Rx only for open pyometra in stable breeding bitches.
| Finding |
Description |
| Signalment |
Middle-aged to older intact bitch, 1-2 months post-estrus |
| Clinical Signs |
Purulent vaginal discharge (open), lethargy, anorexia, PU/PD, vomiting |
| CBC |
Neutrophilia with left shift (or neutropenia if severe) |
| Imaging |
Tubular soft tissue in caudal abdomen; US: enlarged uterus with fluid |
Canine Brucellosis (Brucella canis)
Brucella canis is the most important infectious cause of canine infertility. This is ZOONOTIC and REPORTABLE.
Clinical Features
Diagnosis and Management
- RSAT: Screening (sensitive, high false-positive rate)
- AGID: Confirmatory (more specific)
- Blood Culture: Gold standard
- NO CURE: Treatment = sterilization + long-term antibiotics (doxycycline + aminoglycoside). Infection is lifelong.
Memory Aid - "BRUCE": Breeding failure, Reportable/zoonotic, Untreatable (no cure), Culture is gold standard, Epididymitis in males
| Treatment |
Protocol |
Considerations |
| OHE (TREATMENT OF CHOICE) |
Surgical removal after IV fluid stabilization |
Curative. Recommended for all cases |
| PGF2alpha |
Dinoprost 0.1-0.25 mg/kg SC for 3-5 days |
Open pyometra only, breeding value. Side effects: V/D |
| Aglepristone |
10 mg/kg SC days 1, 2, 7 |
Not available in USA. Fewer side effects |
Male Infertility (Stud Dog)
Stud dog fertility peaks at age 5. Evaluation: history, physical exam, and semen analysis.
Causes of Male Infertility
Semen Analysis Parameters
High-YieldSpermatogenesis takes 62 days. After testicular insult, expect 60+ days for recovery. Primary defects (head) = testis origin; secondary (tail) = epididymis.
| Feature |
Description |
| Transmission |
Venereal (primary), oronasal, transplacental |
| Female Signs |
Late-term abortion (days 45-55), embryonic death, infertility |
| Male Signs |
Epididymitis, orchitis (acute swelling, chronic atrophy), infertility |
| Non-Reproductive |
Lymphadenopathy, discospondylitis, uveitis (rare) |
| Category |
Causes |
Findings |
| Prostatic |
BPH, prostatitis, cysts, neoplasia |
Prostatomegaly, hematospermia |
| Testicular |
Orchitis, degeneration, neoplasia |
Asymmetry, soft/firm testes; oligospermia |
| Infectious |
Brucella (ALWAYS rule out), Mycoplasma |
Epididymitis, positive serology |
| Environmental |
Heat, medications, phytoestrogens |
Reversible; recovery takes 60+ days |
| Parameter |
Normal |
Clinical Significance |
| Volume |
1-30 mL |
Low = incomplete collection or prostatic disease |
| Concentration |
Greater than 200 million total |
Oligospermia = testicular dysfunction |
| Motility |
Greater than 70% |
Low = epididymal dysfunction |
| Morphology |
Greater than 80% normal |
Head defects = testicular; tail defects = epididymal |