2.6 Stallion repro and AI

When does testosterone production start in a stallion?

6+ months → start developing coltish behaviour

When are measurable numbers of mature spermatozoa in the ejaculate first seen?

14-18 months

• production from 12 months

When is stallion full sexual maturity achieved?

2-3 years

Main difference of stallion and mare reproduction

Stallion is less affected by seasonal production → can be fertile all year

• but still some effect → less semen in short days

Where is the ampulla and what is it for?

• Swelling at termination of vas deferens (neck of bladder)

• Spermatozoa storage

What are the vesicular glands for?

Making gel fraction of ejaculate

What is the prostate gland for?

Making watery seminal plasma + pre-ejaculatory fluid

What are the bulbourethral (Cowper’s) glands for?

Small contribution towards seminal plasma

How long does equine spermatogenesis take?

57 days

• therefore takes 57 days to recover fertility from repro tract injury

3 stages of equine spermatogenesis

• Spermatocytogenesis (mitosis)

  • Primary spermatocytes

• Meiosis

  • 4 haploid spermatids

• Spermiogenesis

  • Differentiation into mature spermatids → released as spermatozoa

3 constituents of semen

• Watery pre-ejaculatory fluid (from prostate)

• Rich, creamy seminal fluid (with spermatozoa)

• Gel like postejaculatory fraction (from vesicular)

  • Ensures fluid does not leak out of female

• (contaminants)

3 places in which the total number of spermatozoa are stored

• Ampulla

• Vas deferens

• Caudal epididymis

7 things to examine for stallion breeding soundness

• Signalment and history

• General health (especially orthopaedic and neurological soundness)

• Previous breeding history

• External genitalia exam

• Accessory sex glands and inguinal ring by rectal exam

• Disease testing (serology and swabs)

• Semen collection and exam

Which 2 diseases have to be checked for annually in serology?

EVA and EIA

Which 3 sites are swabbed for pathogens?

2 sets of swabs at 7+ day interval:

• Penile sheath

• Urethral fossa (where smegma accumulates into ‘bean’)

• Urethra

• (pre-ejaculate if possible but often need mare assistance)

What 3 pathogens are tested for in swabs?

• CEM (Taylorella equigenitalis)

• Klebsiella

• Pseudomonas

Main thing to look out for when collecting semen samples

Collect gel free sample (use filter to separate) → gel slows sperm down which affects motility testing

3 considerations for checking sperm motility

• Motility only reliable up to 30mins after collection

• Warm the slide

• Keep extended sample to check motility over time

Which type of motility should be measured in horse semen? What value does this usually have in fertile stallions?

Progressive motility → some might be moving but not in a progressive direction

• 60%+ is good

Why is artificial insemination not always used in horses?

Banned in thoroughbred racing industry

3 benefits and 4 drawbacks of artificial insemination

• Less work for stallion for greater number of insemination

• Preferable for competition stallions (so they don’t learn to act up when seeing a mare in competition)

• Semen can be stored and transported to mare not in same place

• Reliant on transport links

• Reliant on equipment and expertise

• Cannot be used for racing thoroughbreds

• Lower conception rates

In hand cover insemination, how do you know when ejaculation has happened?

Stallion exhibits tail flagging

2 types of artificial vaginas

Colorado and Missouri

Why should chilled semen not be warmed before insemination?

Minimises changes in semen temperature

Why is insemination outside of oestrus potentially harmful? What 2 substances can be given to a mare to induce ovulation?

• Risk of endometritis

• Deslorelin (GnRH analogue)

• hCG

5 pathogens checked in chilled and frozem semen

• Contagious equine metritis (Taylorella equigenitalis)

• Klebsiella pneumonia (capsule types 1, 2, 5)

• Pseudomonas aeruginosa

• EIA

• EVA (vaccine or seronegative for equine arteritis virus)

When should chilled and frozen semen be inseminated in relation to ovulation?

• Chilled → inseminate before ovulation

• Frozen → inseminate no later than 6 hours after ovulation

Progressively motile sperm percentage in stallion

>75%

Progressively motile and morphologically normal sperm percentage in stallion

>50%

Definition of subferility (2)

• Conception rate of <30% per cycle

• Pregnancy rate of 10-60% per season

Tool and healing method in stallion orchiectomy

• Emasculators

• Second intention → aftercare needed for open scrotal wounds

In which 2 types of stallions are orchiectomies not done?

• 5+ years old

• Breeding stallion