Lecture 27: Stallion Infertility

How do equine breeding injuries occur?

- Kicked (body, penis, testicle)

- mount over wall or fence (body or genitalia)

- leg caught in breeding hobbles

- injury to penis during collection on a phantom (artery rupture or penis soft tissue damage)

What is the venous plexus like in a stallions?

- on dorsal surface of the penis and looks like non-uniform swelling

What are methods to support the penis?

- gauze

- tubing

- mesh

What is the testicular degeneration like in stallions?

- commonly in older stallions often caused by age and thermal injury

- testicle was once normal size and is now smaller

- can be unilateral, bilateral, temporary or permanent

What are causes of testicular degeneration?

- thermal injury = common cause

- age = most common cause

- low concentration, high morphological defects (primary defects)

- parasite migration

- blood flow issues

- vasculitis

What are thermal injury causes of testicular degeneration?

- systemic infections

- prolonged increase in ambient temperature

- scrotal insulation (edema, dermatitis, hemorrhage

- conformational factors leading to incompetent heat exchange system

What are common age related problems that can result in testicular degeneration?

- gradually developing vascular lesions

- changing in sertoli cell function (initially seen)

- pituitary dysfunction

How can you diagnose testicular degeneration?

- GnRH challenge - single vs multiple

- hCG = lower than normal response

- testicular biopsy

- measure testosterone, estrogen, FSH, and inhibin

How do you use testosterone, estrogen, FSH, LH, and inhibin to diagnose testicular degeneration?

- normal LH and testosterone

- increased FSH

- decreased inhibin and estrogen

How do you differentiate testicular degeneration from testicular hypoplasia?

- hypoplasia = testicles are just small

- testicular degeneration = needs to have normal size, texture, and functional testicles at some time in life

What is mild testicular degeneration like?

- normal or slightly small testicle

- slightly soft to soft consistency

What is severe testicular degeneration like?

- marked decrease in testicular size

- firm consistency

- as volume decreases the tunica albuginea become palpably wrong

What are testicular torsions like in stallions?

- sudden onset of pain (never forget to check the testicles of a stallion that present for colic)

- commonly in standardbreds

- condition tends to recur

How do you diagnose testicular torsion in stallions?

- IDing the position of the tail of the epididymis

- U/S

How do you treat testicular torsion in stallions?

- uni/bilateral orchiectomy

When you palpate the entire length of the epididymis what do you normally feel?

- epididymal body is loosely attachedon the dorsolateral aspect of eachtesticle

- epididymal tail and ligament of the tail of the epididymis should be palpable to determine orientation

- Soft spongy texture

- Not uncommon to have one testes 180* rotated without CS

What are causes of orchitis in stallions?

- traumatic

- infectious (usually hematogenous)

- parasitic (strongylus edentatus)

- autoimmune (damaged blood/testes barrier)

How can you treat orchitis?

- long term antibiotics and NSAIDs

- Acute cases +/- hemiorchidectomy/hemicastration due to risk of damaging other testis (rare)

What is epididymitis?

- primary bacterial epididymitis is uncommon in horses

- most commonly associated with Strep equi zooepidemicus

- can show no signs, lethargy, inappetance, or abd pain

How do you treat epididymitis?

- unilateral orchidectomy/hemicastration

(poor response to abx)

What is the most common testicular tumor in older stallions, >2 years?

Seminoma

- Germ cells

- Usually diagnosed in sexually mature males

- Pale, soft, lobulated

What is the most common testicular tumor in younger stallions,

Teratoma

- Pluripotent stem cell

Testicular tumors are commonly painless and have an insidious onset. What is the prognosis like?

- good with castration, due to low metastatic rate

- poor for fertility = impacts thermoregulation

Where do you need to examine for extension of testicular tumors?

- spermatic cord

What is the most common neoplasia of the equine penis/prepuce?

- squamous cell carcinoma

What is the second most common preputial tumor in stallions?

- saroids

What are squamous cell carcinoma like in stallions?

- most common neoplasia of the penis/prepuce

- more common in geldings

- small plaque to shallow roughened ulcerated lesions

- looks like a lot of things = need bx

What is the cause of summer sores?

- habronema muscae larval

What are summer sores?

- most commonly on the urethral process or preputial

- larvae stimulate granulomatous reactions --> yellow caseous granules

What is the treatment for summer sores?

- ivermectin

What can paraphimosis be like, which is usually caused due to trauma, acepromazine, exhaustion, or damage?

- inflamed prepuce that displaces ventrally and can't retract penis

- penile prolapse and paralysis

- flaccid penis that is unable to retract into the prepuce

How do you handle a horse with paraphimosis?

- important to support penis ASAP

- prognosis progressively worsens as condition persists

- TX can be a lot of things like support. but if fails to respond may need to castrate or amputate

What is phimosis?

- Retention of penis within prepuce, can't extend penis from the prepuce

- will dribble urine

- tx with surgical transection

What is priapism?

- unnatural penile tumescence = erection that won't go away due to blood becoming sludged in the penis

- due to inflammation, spinal cord problems, phenothiazines, purapura, ect

How do you treat priapism?

- penile support

- flush corpus cavernosum

- shunt

- cholinergic blocker

- phallectomy

- retraction of suture

What is proud cut?

- an old wives tail since hard to cause

- stallion is castrated but some testicular or epididymal tissue is left behind that results in a gelding exhibiting stallion like behavior

How do you test for proud cut in stallions?

- hCG stimulation test

What could result in retained sexual behavior of a gelding?

- If cut after a sexual experience

- castrated at an older age that has performed pasture breeding with mares

- leaving a portion of epididymis does not allow for testosterone production