Stallion Infertility

Question 1

What extrinsic factors may affect fertility?

Answer 1

• Unrealistic expectations
• Reproductive Management
  
  • Timing of insemination
  • Breeding technician
  • Handling of semen
  • Collection processes
  • Ensure mare is in good pre-breeding condition
  • Normal estrous cycles with no problems
  • Bred at the optimal time
  • Adequate pre-breeding and post-breeding veterinary care
  • Early pregnancy diagnosis
  • If not pregnant make sure mare is returned at the appropriate time

Question 2

What non-infectious causes affect fertilty?

Answer 2

• Poor libido
• Failure to ejaculate
• Toxic properties of seminal plasma on sperm
• Trauma
• Sperm accumulation
• Hemospermia
• Urospermia
• Pychological
• Inability to mount and copulate
• Penile dermatological conditions
• Endocrine abnormalities

Question 3

What causes failure for stallion to ejaculate?

Answer 3

• Behavioral or physical
• Evaluate each component of breeding process
  
  • AV preparation
  • Phantom height, width
  • How the stallion is handled
• Try breeding to submissive mare showing prominent estrus in a controlled environment
• Perform thorough physical, neurological and lameness exams
• Attempt different techniques and AV

Question 4

What is Oligospermia?

Answer 4

<500 x 10⁶ per ejaculate

Question 5

What is Azoospermia?

Answer 5

• Measure alkaline phosphatase of the seminal plasma
  
  • ALP produced in the epididymis
• >1000 IU/L suggestive of true ejection
• 100 - 1, 000, indicates partial ejaculation
• <100 IU/L indicates ejaculatory failure or blockage
• Most normal stallions >3,000 IIU/L

Question 6

What is Paraphimosis? Causes? Treatment?

Answer 6

• Penile prolapse and paralysis
• Unable to retract penis into the sheath
  
  • Inhibits normal blood flow
  • Further swelling and edema
• May result from:
  
  • Trauma to the penis
  • Trauma to the 3rd or 4th sacral nerve
  • Phenothiazine derivatives (Acepromazine)
  • Severe debilitation
  • Neurological conditions
    
    • Neurotropic form EHV-1
    • EPM
• Critical to support the penis immediately
  
  • swelling and edema can rapidly progress to ulcerations
  • without aggressive therapy, amputation or euthanasia will be required
• Failure to respond to treatment often leaves the penis cold and insensitive
• Excoriation of the skin may occur
• Treatment:
  
  • Stall confinement with some controlled hand walking
  • Sling support of the penis
  • Reduce edema and replace penis into the sheath
  • Hydrotherapy 20-30 minutes 2-4x a day
  • Systemic Therapy:
    
    • Glucocorticoids
    • NSAIDS
    • Systemic antibiotics
    • Diuretics
    • Gastroprotectants

Question 7

What is Priapism?

Answer 7

• Erection in the absence of sexual stimulation that does not regress
• Clotted/sludged blood develops within the corpus cavernosum due to disturbance in venous outflow
• Early medical management
  
  • NSAIDs
  • Massage
  • Sling support
  • Diuretics
  • Benztropine mesylate: 8mg IV
    
    • anticholinergic
    • for cases caused by phenothiazine derivatives
• Treatment:
  
  • lavage of the corpus cavernosum penis
    
    • Standing or under general anesthesia
    • Heparinized saline until the effluent is clear
      
      • 2-4 liters
    • When efflux is cleared penis relaxes
    • Management to prevent recurrence
  • Aggressive surgical management:
    
    • Shunt between corpus cavernosum and corpus spongiosum
    • Phalectomy and castration

Question 8

What is Sperm accumulation?

Answer 8

• Accumulation of sperm within the Ampullae
  
  • estimated to affect 30-40% of stallions
• Dx:
  
  • Sperm numbers and quality in ejaculate
    
    • Variable between ejaculates
      
      • most commonly very large #s with poor motility and morphology
    • Complete ampullae blockage could result in azoospermia
  • Rectal palpation & US of ampullae
• Tx:
  
  • Frequent massage of the ampullae
  • Frequent breeding and collections
  • Stimulate smooth muscle contractions
    
    • Oxytocin 10-30IU IM

Question 9

What is Testicular Degeneration?

Answer 9

• Recognized by:
  
  • reduced fertility
  • reduced testicular size
  • reduced semen quality
• Unilateral or bilateral, temporary or permanent
• Acquired form or Idiopathic Form
• Dx:
  
  • Hx of decreased fertility
    
    • sudden or gradual
  • decreasing testicular size
    
    • disproportionally large epididymis
  • Softening of the testing parenchyma
  • semen evaluation
    
    • low daily sperm output
    • increased immature round spermatogenic cells
  • Hormone profile
  • Testicular biopsy
• Tx:
  
  • No treatment options for idiopathic and moderate to severe degeneration
  • Removing the inciting cause may allow recovery in mild cases
  • Acquired cases may not progress once inciting cause is removed
  • Stallion management:
    
    • Adjust breeding book based on the actual DSO
    • Allow sexual rest between breedings
    • Proper mare management so that only one breeding is required per cycle

Question 10

What are causes of Acquired Testicular Degeneration

Answer 10

• Heat, cold, loss of thermal regulation, radiation, toxins, ischemia, nutritional deficiencies, exogenous androgens, systemic infection, autoimmune disease and neoplasia
• focal insults results in focal or unilateral degeneration
• systemic insults result in bilateral or diffuse degeneration
• removal of the inciting cause can result in recovery with mild degeneration

Question 11

What is Idiopathic Testicular Degeneration

Answer 11

• Most commonly seen in middle-aged to older stallions
• Typically bilateral, progressive and permanent/untreatable
• Primary problems lies at the level of the testis
  
  • Decreased inhibin levels point to sertoli cell dysfunction
• Sertoli cell dysfunction leads to generalized testicular dysfunction and endocrine imbalance
  
  • Decreased inhibin, estrogens
  • Increased FSH
  • Normal LH and testosterone

Question 12

What is Urospermia?

Answer 12

• Behavioral or lack of bladder sphincter control
• Poor to no motility of sperm, yellow color of semen, urine odor
• Typically urinate during the final ejaculatory pulsations
• Dx:
  
  • Urea Nitrogen >30mg/dL
  • Creatinine >2mg/dL
• Management:
  
  • Attempt to collect after urination
  • Collect using an open ended AV and collecting the fractions separately

Question 13

What are infectious causes of Sub/Infertility

Answer 13

• Systemic Infections:
  
  • Reproductive tract
    
    • Epididymitis
    • Orchitis
    • Testicular abscess
    • Seminal Vesiculitis
  • Pyrexia
• Infections of external genitalia
  
  • Pathogenic bacteria
    
    • pseudomonas aeruginosa
    • Klebsiella pneumoniae
    • Streptococcus zooepidemicus
    • Tayloreela equigenitalis (CEM)
  • Viral
    
    • Equine Viral Arteritis
    • EHV-3