Lesson
8
Diseases
of the Reproductive System of the Mare and Stallion
MARE INFERTILITY
What
is normal fertility?
1. ~50% pregnancy rate – single estrus.
2. ~80-85% pregnancy rate - mares bred in a season.
3. A
pregnancy loss of ~10-12% will occur on a well managed horse farm.
4. If have
100 mares, the average will be 80 to 85 pregnant mares at 40 days and 70 to75
will produce live foals.
5. Early
embryonic loss is the major factor in fertility losses in sub-fertile mares
(60-70% loss prior to day 14.)
I.
Non-infectious causes of infertility
A. Mare is not in heat, so we assume she can’t be
bred.
1. Pregnant (be sure and rule this out in all
situations).
2. Persistent corpus luteum (CL) After ovulation the ovarian follicle is
replaced by a reddish-yellow mass called the corpus luteum (yellow body). The
corpus luteum secretes the hormone progesterone that causes the mare to stop
being receptive to stallions.
B. Mare is sterile and unable to conceive.
1. Genetic abnormalities.
C. Out of season
1. Transitional phase.
2. Winter Anestrus (remember about 15 –20% of mares
will cycle year around.)
3. Treat – Light program (16 hours of light daily).
4. Ovarian shutdown.
a. Usually occurs in a small percentage of mares
(1-2%) that have just foaled. (breed these mares every
other year)
b. Mares of 25 years of age or older.
c. Nutrition induced (low body condition score –
negative energy balance).
D. Behavioral Anestrus
1. Silent heat.
a. May not like the stallion.
b. Protective of foal.
c. New environment (newly arrived mares).
d. Treat – Palpate if suspicious of silent heat – make
sure she is not pregnant.
E. Anatomical Defects
1. Tilted vulva, sunken anus.
2. Urine pooling.
3. Windsucker.
4. Cervical adhesions or cervical tears.
5. Anything that will block the ability of the sperm
to travel up the tract to meet the ovum.
F. Tumors or cysts associated with reproductive
tract.
1. Granulosa cell tumor.
a. Mare acts like a stallion (tumor produces
testosterone).
b. Extremely large ovary (could be size of a
basketball).
c. Treat – surgical removal - opposite ovary will
start functioning normally.
2. Melanoma.
a. Old Gray mares.
b. Usually just causes irritation of reproductive
tract.
3. Uterine cysts.
a. Older mares.
b. Treatment - laser removal improves fertility.
II. Infectious Causes of infertility
A. Endometritis (metritis/uterine infection).
1. Inflammation or infection of the inner lining of
the uterus.
a. Bacterial - most common.
b. Fungal
2. Diagnosis
a. Culture and sensitivity pre-breeding
i.
Routine--33% of normal mares culture positive during estrus.
ii. As
a requirement by breeding farm on all barren or maiden mares.
b. Culture and sensitivity in problem mares
i. If
a mare fails to conceive after two cycles.
ii. If mare is showing abnormal discharges.
ii. On palpation or ultrasound- doughy, thickened
uterus, fluid in uterus, or lack of normal involution in the foaling mare.
3. Treatment Options
Intrauterine infusions of appropriate antibiotics
(according to sensitivity testing) (60 to 500 Milliliters)
Intrauterine
lavage – large volumes of sterile saline to flush debris out of uterus and
stimulate normal uterine immunity (1 to 2 liters).
a. Prevention – good hygiene in breeding shed, in
chute area and at foaling.
b.
Make sure there is no venereal disease transmission from stallion to mare.
Broodmare Management
I. Internal Reproductive Exam
A. Rectal Palpation
1. Palpate ovary size, shape, and function
(follicles, CL)
2. Palpation of both uterus and cervix.
a.
tone of uterus, pregnancy status (18 – 22 days is earliest ), size.
b.
cervix – open or closed.
B. Ultrasonography
1. Rectal exam with ultrasound probe in palpating
hand.
2. Can examine ovaries, uterus, cervix, early
pregnancy (14 to 16 days).
C. Vaginal speculum exam
1. Status of the cervix
a.
open , relaxed, edematous (swollen), and moist – estrus.
b.
closed and dry – pregnancy or diestrus, or anestrus.
2. Determination of urine pooling in vaginal vault.
a. Usually in older mares.
b. Some urine is not excreted to the outside, but
splashes back and pools in the vagina. (often
responsible for infertility).
c. Candidates for surgical correction to prevent
problem
3. Uterine fiberoptic exam
a. Not routine. Only done for
examinations of the internal structures of the uterus for diagnostic purposes.
4. Uterine Biopsy
a. Use of a biopsy instrument to gather a small
sample of uterine tissue.
b. Microscopic exam of this tissue by a pathologist.
c. Biopsy classified in 3 basic categories:
i.
Kenney type 1 –Normal. Should not have a problem getting
pregnant or carrying a foal to term.
ii. Kenney type 2 –Evidence of mild infection or
inflammation that should be able to be cleared up with correct therapy, and mare would be considered to be able to get in
foal and carry to term.
iii. Kenney type 3 – Evidence of scar tissue damage
to uterus and previous damage to tissues that would make it difficult for this
mare to conceive or carry to term. (less than 10%
chance of being fertile).
5. Uterine Culture and sensitivity
a. Use of a sterile swab that is introduced into the
uterus and a swab sample is taken from the uterus.
i.
Sent to laboratory to attempt to grow microorganism (bacteria) on gel agar
plates, identify the microorganisms, and determine susceptibility to
antibiotics.
ii. Common Pathogenic bacteria isolated:
(a. E. coli
(b. Beta-hemolytic streptococcus
(c. Klebsiella
(d. Pseudomonas
II. Practical Farm Practices with Mare Management
A. Pregnant Mares
1. Carry through foaling and determine status at
foal heat for rebreeding.
a. Foal heat is 9 days post foaling.
i. If
uterine involution is good at this stage, the mare is healthy, consider
breeding.
ii. Heat after 9 day heat is 28 -30 days from
foaling. Conception rates are higher if wait to be bred at this time.
B. Barren mares (did not conceive or aborted last
breeding season)
1. Begin in late fall to examine these mares and
clear up any infections, urine pooling, poor vulvar conformation (caslicks) or other problems.
2. Consider putting these mares under lights (16
hours per day from December to March).
C. Maiden mares
1. Examine at the beginning of breeding season for
normality of reproductive tract.
2. Open hymen if necessary.
3. Open caslicks if
necessary.
4. Use light to go through transition phase of cycle
on these mares. (same as barren mares).
III. Management concerns in the broodmare during breeding
season (this includes all mares to be bred and undergoing an estrous cycle.)
A. Irregular Cycles
1. Mares
going through the transition phase (were not put under lights).
a. Put on REGUMATE for 14 days: when taken off, some
may begin cycling normally.
b. Transition phase mares are very hard predict. May just have to wait out the transition phase.
2. Persistent
heat
a. Normally caused from transition phase.
b. An excessively long fertile heat can be dealt
with by using Human Corionic gonadotropin (HCG) 2500
units. (2 ½ cc of a 10 cc vial) This will normally cause ovulation within 24 to
48 hours.
3. Prolonged diestrus (persistent corpus leteum)
a. The CL continues to produce progesterone and possibly
the prostaglandin level of the mare is not high enough to cause luteolysis.
b. Injection of prostaglandin product (lutalyse) will destroy the CL and the mare will show estrus
within 2 to 3 days. This will be a fertile heat.
c. Early embryonic death may cause a prolonged diestrus. Prostaglandin would be used in this case also.
d. BE
B. Silent Heat
1. Detected when records indicate the mare should be
in heat (9 day heat, or 16 to 18 days since last heat and mare is not
pregnant.)
a. Palpation to determine if mare is showing
physical evidence of heat (estrus), is pregnant, or possibly has a persistent
CL.
b. Silent heat normally seen in mares with first
foals and over protective dams.
c. Rectal palpation to determine breed able
follicle, artificial insemination, or tranquilization and live cover. Allow mare to see her foal during the
breeding process. Take extra time to
tease mare and reassure her that her foal will be okay.
C. Anestrus During Breeding
Season (mare stops cycling)
1. MAKE
2. The occasional mare that foals will stop cycling
for no reason. These mares appear to be every other year mares. They usually continue
to show this characteristic throughout their lifetime.
3. Early embryonic death in mares cause
many to fail to come back into regular cycling. Prostaglandin will usually work
to bring them back in if it is not more than 45 days since the mare was bred.
D. Stallion-Like Behavior in the Mare
A. Normally
caused by granulosa cell tumor on the ovary.
Granulosa cell tumors produce testosterone. These mares are infertile until the tumorous
ovary is removed.
B. Can
normally be diagnosed by behavior signs and palpation of ovary (these tumorous
ovaries can become very large).
E. Endometritis -- (uterine infections)
This
subject is covered under fertility in the mare.
Stallion Infertility
DEFINITIONS:
Infertility
– reduced ability of stallion to impregnate a mare.
Sub-fertility
– same as above
Sterility
- complete and permanent loss of the sperm’s fertilizing capacity
or of the stallion’s ability to produce sperm.
Impotency
– term used to describe the stallion’s reduced ability, complete inability, or
lack of desire to perform the breeding act.
Causes of
Infertility in the Stallion
I. Drugs:
A. Testosterone and /or anabolic steroids
1. With long term or excessive use these drugs will
inhibit the normal negative feedback system in such a way as to inhibit the
normal production of Interstitial Cell Stimulating hormone (LH) and
Spermatogenesis Stimulating Hormone (
a. Other drugs, especially ones causing severe side
effects such as diarrhea, loss of appetite or an allergic reaction, could be a
cause for infertility in the stallion.
II. Overuse:
A. Overuse is a potential cause of infertility and
impotency.
1. Young stallions more prone to overuse.
2. Daily breeding of the average, aged stallion will
lower the concentration of the stallion sperm per ejaculate, but should not
lower the total number of sperm produced per day. (leads
to higher volume of sperm, with fewer sperm per milliliter of semen).
3. Every other day breeding in the average, aged
stallion will not decrease the concentration of the sperm produced at
each ejaculate.
4. In A. I. operation, every other day collection is
ideal.
5. In live cover operation with full book of mares,
although it depends on the individual stallion, the average, aged stallion
should be bred no more than 6 – 8 times a week.
III. Painful Breeding:
A.
Injuries to the limbs, especially hind limb problems (hock or stifle lameness)
may cause the stallion to hesitate or refuse to breed.
1. Medication and/or corrective shoeing may be
necessary to manage the injury.
B. Painful problems associated with the reproductive
organs. Injuries to the penis.
1. Care must be taken when using stallion rings, and
when washing and handling the penis before and during breeding and collection.
C. Excessively rough handling by the stallion
handler, or an uncooperative mare.
1. Behavioral problems must be addressed efficiently
and without causing more behavioral problems.
IV.
Season of the Year:
A.
Stallion is also affected by length of light in the day.
1.
During the fall and winter months the stallion will have a longer reaction
time, longer time from initial sexual stimulation and mounting, and will have a
greater number of mounts required per ejaculation. (Libido decreases during
this time)
2.
Semen quality will be slightly less during this time.
V.
Genetic Aspects:
A.
Behavioral as well as physical characteristics for sufficient breeding ability
or potential is genetically endowed.
B.
Hormonal abnormalities can be genetically endowed.
C.
Cryptorchidism –Failure of one or both of the testes to descend into the
scrotum.
VI.
Diseases:
A.
Hereditary disease associated with the reproductive organs
B.
Testes
1. Orchitis –infection or inflammation of the testicle can be
caused by a number of infectious diseases.
2.
Tumors – can occasionally affect one or both testicles.
3.
Trauma by physical blow (mare Kicking) will affect fertility negatively.
C.
Penis
1.
Irritation or localized infections could be a problem.
2.
Tumors (melanoma, or squamous cell carcinoma) will
affect fertility negatively.
D.
Urethra
1.
Infection can be introduced from an infected mare into the stallion’s urethra
and cause the stallion to become infected. This infection can travel to the
accessory sex glands, the vas deferens, the epididymis and the testicle itself.
a. A
healthy stallion can usually resist this infection from becoming permanent, but
will be able to transmit in to other mares during live breeding or A.I. until
his immune system clears it from his system.
A.
Physical trauma to the external genitalia is probably the most common problem
seen in the stallion. It can cause a
temporary infertility or impotency during the breeding season.
1.
Breeding shed accidents
a.
Best prevented by good management and anticipation of possible problems. (Use
of hobbles, routine breeding shed activities, proper stallion handling).
b.
Penile hematoma – a blow to the penis or bending of the penis while it is erect
will cause a rupture of the blood vessels within the tissues of the penis.
VIII.
Semen Abnormalities:
A.
Volume – normally not a critical issue with fertility. Concentration (number of sperm per ml. of
semen) is the determining factor in fertility of the stallion.
B.
Color – blood in semen renders the semen useless. (blood
or pus in the semen causes infertility). Pus may also discolor the semen, and
would indicate infection within the reproductive tract.
C.
Density – semen that is too thick and gelatinous or to thin and watery
indicates malfunction of the accessory sex glands.
D.
Motility – if collection and handling techniques did not cause the reduced
motility, some problem within the stallion is to blame. This would cause
infertility if found to be less that 50% progressively motile sperm in the
sample.
E.
Longevity – if not caused by collection and handling techniques reduced
longevity of the sperm will reduce the sperm’s chances of fertilizing the
mare’s ovum.
F.
Morphology – abnormal sperm cells. Semen samples that contain less than 65%
normal sperm cells are directly related to reduced
fertility.
G.
Live/Dead percentage--if a semen sample contains less than 60% live cells in a
fresh sample, fertility may become affected.
H.
Sperm numbers – the reduction in the number of viable sperm cells per ejaculate
may be due to seasonal variation, overuse, testicular degeneration, or
increased testicular temperature. Sperm concentration normally ranges from 30
million to 600 million sperm per milliliter and that at least 100 million
progressively motile sperm are needed for acceptable conception rates. The
average concentration of a stallion is 50 – 250 million per ml.
I. pH
– An increase in the semen pH (normal is 7.0 –7.8) may be caused by presence of
urine or by infection within the reproductive tract, or by overuse.
J.
White blood cells – Although some white blood cells may be found in a semen
sample, a greater than 1500 WBC per cubic milliliter) usually reflects
infection within the reproductive tract and infertility.
Stallion
Evaluation
I. Stallion Selection:
A. Genetic potential – quality traits that can be passed on to his
offspring.
B. Willingness to cover mares and physical ability to settle them. (individual libido and fertility)
II. Reproductive Exam:
A. Experienced veterinarian or
equine reproduction specialist.
1.
Overall general health exam
2.
Medical history
3.
Disposition (libido)
4.
Physical exam of reproductive anatomy.
5.
Physiological exam involving observation of the breeding process as well as
semen evaluation.
a.
Volume of semen per ejaculate
b.
Concentration of sperm in semen
c. pH of semen
d.
Motility of sperm cells
e.
Morphology of sperm cells
f. Live – dead percentages
g.
Longevity
h.
Contamination (wbc’s or rbc’s present)
Normal Semen Parameters
Volume: 30-250 ml.
Concentration: 30-600 million
(10 to the 6th) /ml.
pH: 6.9 to 7.8
Morphology: at least 65% normal
Live/dead count: at least 65%
live cells
Motility: at least 40% actively
motile (moving in a straight line)
Longevity: at least 40-50% live after 3 hours at room temperature; at least 10% live
after 8 hours at room temperature.
I.
Stallion Vices:
A. Vices dangerous to the
handler or mare
1. Overly aggressive behavior
(savaging mares or handlers)
2. Biting (muzzle or protective
leather pad for mare)
3. Rearing and striking (nose
chain or lip chain)
B. Vices dangerous to stallion
1. Self mutilation (muzzle or
neck cradle-increased exercise or companion)
2. Cribbing and windsucking
(cribbing strap). (A diet with no long
stem roughage can lead to wood chewing.)
3. Weaving and stall walking
(exercise or obstructions in the weaving or walking path or a companion.
C. Vices detrimental to breeding
1. Slow breeder (need for
extended stimulation for erection and mounting or repeated mounts to ejaculate)
a. Improper training prior to
breeding.
b. Overly rough handling
c. Overuse of the stallion
d. Prior bad experience in the
breeding shed
D. Masturbation
1. boredom
– exercise or isolation of the stallion
2. stallion
ring or wire brush on belly
Proper
Stallion management
I. Nutrition
A. Well-balanced 12% protein
ration. Adequate vitamin and mineral availability.
B. At least 50% of ration
should be long stem roughage (hay or pasture)
C. Vary energy amount fed (Mcal) with increases in breeding load.
D. Body condition score 6 to 7.
II. Exercise
A. Carefully planned exercise
program to maintain health and fitness
B. Exercise should be continued
during the non-breeding season.
C. Riding, lunging, walker
exercise, or paddock turnout.
III. Housing
A. Two-acre pasture
with adjoining shelter or stall. Safe environment.
B. Important that the stallion
has the ability to visualize the other horses and activities of the farm.
IV. Health care
A. Dental care
B. Preventive medicine. Worming every 3 months. Influenza and Rhinopneumonitis twice a year. VEE,
EEE, WEE, and
V. Hoof Care
A. Normally the breeding
stallion is not shod for the protection of the mare unless other reasons
require shoeing. Regular hood trimming (every 6 –8 weeks) is necessary.
VI. Light program
A. Although not as helpful to the stallion as
the mare, the artificial light program used on the mares (16 hours of light per
24 hour period) will produce some important improvements in the stallions libido and semen volume. It does not seem
to increase the sperm output per ejaculate.
Normal Breeding Behavioral Parameters
Number of mounts per ejaculate:
1.5
Average time to mount: 5
seconds to 3 minutes
Average time to ejaculate: 20
seconds to 1 minute
Breeding time (from onset of
sexual stimulation to completion of breeding): 45 seconds to 5 minutes.
Number of covers per season
depends on choice of breeding procedures.
Percentage of mares pregnant:
65 – 90 per cent.
Percentage of mares actually
foaling: 45 – 80 per cent.