Non-infectious infertility in the stallion Flashcards
Stallion season
Rate of spermatogenesis and hormone production, and therefore libido decrease in winter
Stallion exteroceptive stimuli
Responds to same increases in day length, temperature, food supply as the mare
Stimulated by oestrus mare
Spermatogenic cycle
56-58 days - important if anything has affected spermatogenesis
Components of fertility exam in stallion
General history
General clinical exam
Bacteriology - urethra, urethral fossa, prepuce swabs
Semen evaluation
Congenital fertility problems in stallion (2)
- Chromosomal
- Testicular hypoplasia
Behavioural fertility problems in stallion (2)
- Shyness/psychological problems
- Musculoskeletal pain
Potential fertility problems in stallion (13)
- Congenital
- Behavioural
- Inadequate erection
- Ejaculatory dysfunction/failure
- Overuse
- Testicular/penile trauma
- Testicular torsion
- Priaprism
- Febrile conditions
- Semen contamination
- Neoplasia
- Endocrinological abnormalities
- Testicular degeneration
Chromosomal fertility problems in stallion
Very rare
Testicular hypoplasia
Relatively common
Incomplete gonadal development
Unilateral or bilateral
Usually associated with underdeveloped epididymis
Soft or firm consistency
Olio- or azoospermic
Round cells in ejaculate
Libido usually affected
Shyness/psychological problems in stallions
Most common in young TB stallions
Reasons:
- Dominated by older mares
- used to being punished for stallion like behaviour
- ‘Handler induced’
Leave alone and loose in yard with 2-3 oestrus mares
Try outdoor covering
Anxiolytic drugs e.g. diazepam
GnRH causes increased LH secretion
Musculo-skeletal pain in stallions
Particularly hind leg and back
Causes a drop in libido, ability to mount etc.
Inadequate erection
Difficult to differentiate from poor libido
GnRH may help
PGF2a may assist erection
Ejaculatory dysfunction/failure
Usually after 7-10 thrusts
Place hand over ventral surface to confirm ejaculation
Alpha-mimetics and/or beta-blockers can treat organic ejaculatory failure
PGF2a may re-initiate ejaculation process
Xylazine can be used to induce ejaculation
Imipramine has been used
Overuse of stallions
Common in first season TB stallions, may be in ageing stallions with testicular degeneration
Semen is watery and grey, smaller volume, less motile sperm, and much lower concentration of sperm
Reduce covering load, cover each mare only once with good oestrus management, ensure he is well fed
If ageing insert subcut low dose GnRH implant
If not TB consider AI
Testicular/penile trauma
Inflammation, heat, haemorrhage, and swelling of scrotum and/or sheath
Drainage often impeded as well as gravity making the oedema worse
Paraphimosis - the inability to retract the penis back into the prepuce then may occur
Reduce inflammation and try o improve venous and lymphatic drainage
Potential sequelae of penile/testicular trauma
- Production of abnormal sperm
- Production of anti-sperm antibodies
- Intra-scrotal haemorrhage or haematocele leading to permanent testicular damage
- Hydrocele may develop
Testicular torsion
180 degrees - common in ponies, asymptomatic, not a problem
360 degrees - very acute, severe colic, emergency
Priaprism
Persistent penile erection
Use of acepromazine is a risk factor
Treat similarly to paraphimosis
Febrile conditions
General illnesses causing a rise in body temperature for a few days can result in a temporary depression of fertility 1-3 months later
Semen contamination
Haemospermia: trauma, urethritis, accessory gland infection etc. can be diagnosed on visual inspection of the urethral process, palpation and US of accessory glands, endoscopy of urethra. Treat with sexual rest, antibiotics, flush via scope or catheter
Urospermia: a neurological problem, diagnose based on colour, smell, pH, urine crystals. Get the stallion to urinate before covering
Neoplasia in stallions
Squamous cell carcinomas of the penis are relatively common
Neoplasia of the testes are rare - seminoma being the most common, Teratoma is found predominantly in cryptorchid testes
Endocrinology abnormalities in stallions
Check LH and testosterone levels as an indication of normality
Impotent stallions tend to have lower blood concentrations of LH whereas concentrations of testosterone tend to be similar to normal stallions
Slow stallions can be treated with low levels of testosterone or GnRH
