Equis ISSN 2398-2977

Male: ejaculatory dysfunction

Contributor(s): Terry Blanchard, Rob Lofstedt, Graham Munroe, Elaine Watson, Madeleine L H Campbell

Introduction

  • Ejaculatory dysfunction (including ejaculatory failure; azoospermia; oligspermia; urospermia) occurs where there is a failure of events associated with the ejaculatory process, whereby there is non-ejaculatory coitus/semen collection Semen: collection or problems with urine contamination of the ejaculate. This is not uncommon.
  • Cause:
    • Psychogenic: arising from bad experiences at breeding such as injury, other painful incidences or having been reprimanded for showing sexual interest.
    • Organic: where the relevant neural reflexes are disrupted or physically damaged.
  • Signs: stallion mounts mare/dummy mare and is capable of obtaining intromission and thrusting, but fails to ejaculate completely OR stallion ejaculates semen which is urine contaminated.
  • Diagnosis: clinical signs; semen analysis including laboratory testing.
  • Treatment: dependent on problem/cause.
  • Prognosis: dependent on problem/cause.

Pathogenesis

Etiology

Ejaculatory failure

Psychogenic ejaculatory dysfunction
  • The following factors can all override the ejaculatory mechanism by the CNS affecting normal reflexes.
  • Rough handling.
  • Injury or mating accident.
  • Pain.
  • Over booked/too many mares (loss of libido Male: lack of libido).
  • Strange surroundings/handlers.
  • Having been previously disciplined for showing sexual interest Male: mounting/intromission difficulty.
Organic ejaculatory dysfunction
  • Lack of stimulation of afferent pathways, eg due to pneumovagina Vagina: pneumovagina/artificial vagina too loose/too cold.
  • Damage to the dorsal nerve of the penis (causing lack of sensitivity and therefore sensory stimulus).
  • Neurological deficits causing failure of contraction or asynchronous contraction of vertebral smooth muscle.
  • Spermiostasis: blocked ampullae may result in separation of sperm heads, sperm packed into 'plugs'- azoospermia or oligospermia Semen: azoospermia - oligospermia. In this case, some fluids (from the accessory sex glands) may be collected in the artificial vagina, but sperm cells will be absent or much reduced in number.
  • Inadequate erection Penis: erection failure.

Urospermia

  • Urine contamination of the ejaculate (urospermia Semen: urosemen) can occur when reflex closure of the bladder neck (which normally prevents urine entering the urethra during erection/ejaculation) fails.
  • This problem may be present in isolation or in association with neurologic deficits of the hindlimbs. Urine is spermicidal.

Predisposing factors

Ejaculatory failure

Psychogenic ejaculatory dysfunction
  • Over-use of stallion by booking too many mares.
  • Pain:
  • Phantom mare not secure and stable - may exacerbate discomfort from orthopedic problems and exacerbate neurological problems having a negative influence on stallion libido/ability to thrust successfully.
  • Slippery breeding area creating insecure footing.
  • Negative experiences by handlers immediately prior to ejaculation.
  • Having previously been reprimanded for showing sexual interest.
  • Mare that misbehaves prior to ejaculation.
Organic ejaculatory dysfunction
Injury to dorsal nerve of penis can be ascertained by pinching the cranial dorsal aspect of the penis to test for sensation.
  • Oligospermia/azoospermia Semen: azoospermia/oligospermia can occur in stallions who have undergone a prolonged period of sexual rest, and whose ampulla have become consequently plugged (this is why historical attempts to prevent stallions masturbating were counterproductive in terms of fertility - regular ejaculation reduces the risk of ampulla becoming plugged).

Urospermia

  • Can occur in isolation, or may be associated with hindlimb neurological deficits.

Pathophysiology

Normal sequence of ejaculatory events

  • Pre-ejaculatory secretions from accessory glands are sacral-mediated and are mainly derived from the urethral and/or bulbourethral glands.
  • Emission of accessory gland fluid and spermatozoa into the urethra is mediated by thoracolumbar reflexes resulting in contraction of their smooth muscles.
  • Bladder is closed by a sympathetic thoracolumbar reflex contracting smooth muscles of the bladder neck.
  • Ejaculation is mediated by the pudendal nerve and a sacral reflex innervating the bulbocavernosus, ischiocavernosus, and urethralis muscles which forcibly expel spermatozoa from the urethra.
  • Outwardly 7-9 vaginal thrusts are typically required to stimulate emission.
  • Ejaculation is indicated by the stallion's tail flagging with each jet of semen expelled, 5-10 times.
  • The anal sphincter also contracts.

Psychogenic ejaculatory dysfunction

  • Normal sequence is disrupted due to:
    • Pain in back Musculoskeletal: back pain or hindlimbs.
    • Negative breeding experiences; such as rough handling, previous breeding accidents (including being kicked by the mare), unfamiliar environments, sexual overuse can produce negative effects on supraspinal center control.
    • Central nervous system (psychogenic) override of ejaculation.

Organic ejaculatory dysfunction

  • Normal sequence is disrupted due to:
    • Lack of stimulation of sacral spinal reflexes (afferent ejaculatory reflex pathway), ie insufficient penile friction due to, eg incomplete penile erection, inadequate thrusting, pneumovagina or incorrectly adjusted artificial vagina.
    • Malfunction of autonomic nervous system.
    • Plugged ampulla/occluded ejaculatory ducts, causing oligospermia, azoospermia Semen: azoospermia/oligospermia, or even retrograde ejaculation into the bladder.

Urospermia

  • Normal sequence is disrupted:
    • The bladder neck is not closed, allowing urine to enter the urethra from the bladder at the same time as semen enters the urethra, and contaminate the ejaculate.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • McDonnell S M (2001) Oral imipramine and intravenous xylazine for pharmacologically-induced ex-copula ejaculations in stallions. Anim Repro Sci 68, 153-159 PubMed.
  • Brinsko S P (2001) Retrograde ejaculation in a stallion. JAVMA 218, 551-553 PubMed.
  • Watson E (1997) Fertility problems in stallions. In Pract 19 (5), 260-269 (Concise outline of main points) VetMedResource
  • Turner R M et al (1995) Use of imipramine hydrochloride for treatment of urospermia in a stallion with dysfunctional bladder. JAVMA 207,1602-1606 PubMed.
  • McDonnell S M, Blanchard T L, Varner D D (1992) Ejaculation: physiology and dysfunction. in stallion management. Vet Clin North Am Equine Prac 8 (1), 57-70 VetMedResource.
  • Mayhew I G (1990) Neurological aspects of urospermia in the horse. Equine Vet Educ 2, 68-69 VetMedResource.
  • Leendererste I P et al (1990) Successful management of persistent urination during ejaculation in a Thoroughbred stallion. Equine Vet Educ 2, 62-64 VetMedResource.

Other sources of information

  • Colahan P T et al (1991) Equine Medicine and Surgery. 4th edn. American Veterinary Publications Inc. ISBN: 0 939674 27 0. pp 884 (concise summary of main points).


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