The stallion Flashcards
What is a stallion?
An entire male horse over 4yo
What is a colt?
An entire male horse less than 4yo
Describe the normal sexual development of male horses
- Testis normally descended into scrotum at or shortly after birth.
- If not descent may occur up to 24 months of age.
- Puberty occurs at 12-24 months
- Maximal sexual maturity reached at 4-5 years and retained until about 20 years.
How long does spermatogenesis take?
60 days
Semen quality is influenced by a wide range of factors, what are they?
Testicular size
Testicular efficiency
Age
Season
Frequency of ejaculations
General health/injury
Testicular size correlates to?
The amount of sperm
How is seasonality linked to reproduction in stallions?
Horses are “long-day breeders” – this is true of stallions as well as mares
Less semen produced over winter
How is age linked to semen production?
Younger stallions produce less sperm and run the risk of being overworked
With each successive ejaculation the number of sperm …?
Halves
How many mares can a stallion mate?
- Very variable – depends on huge number of factors.
- Sperm output may not be the limiting factor, Libido maybe more important
- 500 million motile sperm suggested as suitable dose for natural service and perhaps 150-500 million for A.I.
- Suggested rates include no more than 15 matings a week or two mares a day .
- Some really busy stallions may mate up to 6 mares in a day.
- A book of 80-90 mares a season is often quoted – but very variable
How is a stallion examined for breeding soundness?
Physical exam of external genitalia
Exam of internal genitalia
Observation of libido and mating ability
Semen evaluation
Testicular biopsy
Stallions are swabbed for which disease?
Contagious equine metritis
Where are stallions swabbed for Contagious equine metritis?
Urethra
Urethral fossa
Penile sheath
Pre ejaculatory fluid – if available
Stallions are vaccinated against…?
Equine viral arteritis
Why are stallions vaccinated against equine viral arteritis?
EVA causes abortion
Stallions (only) become carriers.
Notifiable in Stallions.
Blood test before first use to prove seronegative
Describe the importance of injuries or disease in stallions
- Any type of injury (or disease) that causes orchitis must be considered a career –threatening injury (and therefore life-threatening).
- Any penile injury or disease is career-threatening
- Any systemic illness that causes pyrexia will effect sperm production
How are injuries/disease treated in stallions?
Treat quickly and aggressively to reduce swelling, limit inflammation and reduce heat:
- Anti-inflammatory (Nsaids and perhaps corticosteroids)
- Cold therapy
- Massage
- Support
- Diuretics?
- Topical treatments
How is paraphimosis treated in stallions?
Support a paraphimosis with some kind of truss
Maybe give GA, roll on back, gently but firmly replace penis in sheath and place purse-string sutures across preputial orifice
How is priapism treated in stallions?
Surgically corrected by flushing corpus cavernosum with heparinised saline under GA.(8mg benztropine mesylate iv?) (10mg phenylephrine into C. Cavernosum?)
What are the considerations of colic in stallions?
Take extra care when rectalling stallions – higher risk of rectal tears.
Always check for inguinal herniation, scrotal hernias and testicular torsions as source of colic .
What are the possible implications of dermatitis in stallions?
Scrotal and penile dermatitis may cause sufficient inflammation to affect mating or sperm production
Name some neoplasia that can affect the ability of a stallion to perform
Sarcoids
Squamous cell carcinoma
Melanoma
Seminoma and other testicular tumours
Papillomas
List the advantages of artificial insemination in horses
- Semen can be transported – spreading genetic material
- Semen can be stored – even after a stallions death
- Ejaculates can be divided into smaller doses – more matings
- A.I. reduces risk of venereal disease
- A.I. reduces post mating endometritis
- Semen can be examined readily
List the disadvantages of artificial insemination in horses
- Specialist skills needed to collect, process and inseminate semen
- Conception rates may not equal natural service
- Expensive
- Labour intensive
- Venereal infection still possible
- Not acceptable for Thoroughbred authorities
Describe semen collection from stallions
Requires a dummy mare, artificial vagina, mare in season and skilled handlers.
Maybe hazardous
A.V. needs careful setting up
Describe how to use fresh semen
- Use within few hours
- If stallion is very local or physically unable to mate
- Can be treated with “extenders” (extenders increase lifespan of sperm, and may contain antibiotics to kill pathogens . Extenders are often milk or egg based products)
Describe how to use chilled semen
- Can be transported further afield as can last up to 48 hours
- Mixed with extenders and then slowly cooled to 5o C.
Describe how to use frozen semen
- Semen separated into small doses- 0.25-5ml
- Treated with extenders and cryoprotectants
- Frozen in sealed straws
- Freezing temperatures and cooling rates highly technical
- Stored in liquid nitrogen flasks
- Can keep forever (provided someone remembers to top-up the liquid nitrogen!)
Describe insemination in mares
- Can be carried out by trained para-professionals.
- Fresh and chilled semen introduced through the cervix, from a loaded syringe via an insemination catheter.
- Don’t use rubber bunged syringes – spermicidal!
How is frozen semen prepared for insemination?
Straws warmed to 37C in water bath, dried, unsealed and inseminated via insemination “gun” – either just through the cervix or into the uterine horn on the side of ovulation (deep uterine insemination)
Describe the timing of insemination for fresh and chilled semen
Same as for natural service i.e. Up to 48 hours before ovulation
Describe the timing of insemination for frozen semen
Survival time not as long – best done as close to ovulation as possible (up to 12 hours before or 6 hours after ovulation)
