STALLION
ANATOMY AND
PHYSIOLOGY
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REPRODUCTIVE TRACT OF THE
STALLION CONSISTS OF
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BRAIN
CIRCULATORY SYSTEM
ENDOCRINE SYSTEM
TESTICLES
EPIDIDYMIS
VAS DEFERENS
ACCESSORY SEX GLANDS
URETHRA
PENIS
ASSOCIATED STRUCTURES
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TESTICLES
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OF ABDOMINAL ORIGIN
LOCATED EXTERNALLY IN THE SCROTUM
WITHIN A REFLECTION OF THE PERITONEUM
KNOWN AS THE TUNICA VAGINALIS
CONTAIN GAMETE CELLS AND SPERM STEM
CELLS THAT PRODUCE SPERMATOZOA
TUBULAR SYSTEM OF THE TESTICLE CONNECTS
TO THE…
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EPIDIDYMIS
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BEGINS AT THE CAUDAL END OF THE
TESTICLE
RUNS THE FULL LENGTH OF THE
TESTICLE TO THE VAS DEFERENS
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VAS DEFERENS
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TRAVERSES BACK THROUGH THE
ABDOMEN TO THE CRANIAL PELVIC
CAVITY
CONNECTS TO THE PELVIC PORTION
OF THE URETHRA
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URETHRA
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PELVIC PORTION URETHRA HAS:
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THESE GLANDS PRODUCE THE NONSPERM
PORTION OF THE EJACULATE=
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SECONDARY SEX GLANDS ON EACH SIDE
PROSTATE
SEMINAL VESICLES
BULBAR URETHRAL GLAND
PREJACULATE FLUID
SEMINAL PLASMA
GEL
URETHRA EXTENDS DOWN BETWEEN HIND
LEGS
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TO THE PENIS LOCATED ON CAUDAL VENTRAL ABDOMINAL
MIDLINE JUST AHEAD OF SCROTUM
PENIS CONTAINS ERECTILE TISSUE NECESSARY FOR
COITUS
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Stallion Physiology
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Onset of sexual maturity 10-24 months
Sperm output
 Semen volume/ejaculate, ml 30- 200+cc total output
 Sperm Rich portion usually constant around 45-70cc
 Gel portion changes considerable with teasing and
amount of activity
 Sperm output 6-9 billion (fpm)
 Survival time with fertilizing capacity -1-2 days
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Testis
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Average size – 9x6x5 cm
Total scrotal width > 80 mm
Testicular Parenchyma-90%
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Seminiferous tubules (70%)
Sertoli cells (30%)
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Increases during the long days
Increase with age (2-3, 4-5) and season
Leydid cells (2-12-18%)
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Increase with age (2-3, 4-5, 13-20) and season
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Stallion Physiology
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Up to 70,000
spermatozoa/second
57 days for each cell
Daily production = 3
billion or more
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Age and season
dependent
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Average Testicular Volume for Horse
for Different Ages
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Age (yr)
Total Testicular Volume (ml)
1.0
50
1.5
71
2.0
95
2.5
119
3.0
167
4-5
272
6-12
313
13-20
306
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STALLIONS HAVE ANNUAL
RHYTHM MUCH LIKE MARES
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ASSOCIATED WITH LENGTH OF
DAYLIGHT/DARKNESS
TESTOSTERONE PEAKS @ MIDDLE OF
BREEDING SEASON
TESTOSTERONE DEPRESSED IN
WINTER
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SPERM HAS 3 JOBS TO
ACCOMPLISH FOR SUCCESS
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ONCE PLACED IN
BODY OF UTERUS
BY EJACULATION:
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MOTILITY
CAPACITATION
EXCHANGE OF
CHROMATIN MATERIAL
THERE ARE METHODS
TO TEST MOTILITY,
ACROSOMAL FUNCTION,
AND CHROMATIN
QUALITY
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MOTILITY
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Function of the Middle Piece
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Mitochrondrial Activity
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Consumes Energy
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Must be forward Progressive to be of Value
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Capasitation
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Function of the Acrosome
Releases enzymes that react with the Zona
Pellucida
Takes the enzyme of many sperm to cause
reaction
Sperm are viable for 24hr. After
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Chromatin Transfer
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Function of the Head
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Contains Genetic material
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imperfict Chromatin will result in early
embryo loss
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Semen Has Three Parts
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Pre-ejaculate
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Sperm Rich Sperm and seminal plasma
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Gel
Mucous substance at end of
ejaculation
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Clear lubricant
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Semen output
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30- 200+cc total output
Sperm Rich portion usually constant
around 45-70cc
Gel portion changes considerable with
teasing and amount of activity
Sperm output 6-9 billion (fpm)
Total output change with activity
Maximum Standard use every 8 hr.
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Number of Sperm Depends On:
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Seasonal Influences (Photoperiod)
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Effected Areas
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Ejaculate volume
Sperm numbers
Total sperm/ejaculate
Sperm motility
Willingness to breed
Mounts before breeding
Scrotal size
Testosterone production
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Sperm Dose
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Under Debate
Changes with Breeding Technique
Industry Standard at present is considered
500 million (fpm)
Higher for frozen semen
Lower for specialized
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Semen Extending and Storage
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Use To increase Number of doses per
ejaculate
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Used to increase sperm survival in Fresh
Cooled or Frozen storage
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Centrifugation
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To Increase Concentration of Sperm
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Remove Bacteria
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Remove Seminal Plasma
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Increase Quality in storage
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