Equine Reproduction
Dr.
Jack Sales, DVM
Lesson
Six
Pregnancy Diagnosis and
Management of the Pregnant Mare
In this lesson we will study normal
fetal development in the pregnant mare, and overall management guidelines
involving the pregnant mare. A detailed study of the foaling process is
included.
Assignment: read chapters 7 & 9 of
the text.
MANAGEMENT OF THE
PREGNANT MARE
I. Normal
fetal development in the mare:
the following are important and practical embryonic or fetal stages that
correspond to practical aspects of managing the broodmare.
A. Fertilization of ovum (egg) occurs in the ovi duct (fallopian tube
of the mare.
B. Fertilized ovum transported into the horn of
the uterus at 5 - 6
days.
C. Recovery of embryo at 7 days for embryo
transfer is 64 to 128
cells.
D. A 14-day embryo prevents release of
prostaglandin and can be
detected by ultrasound as a pregnancy.
E. If twinning has occurred, pinching off one
vesicle (embryo) is
attempted at approximately day 18 when the
embryo has fixed
in location.
F. Endometrial cups form by day 45 which release
progesterone
for pregnancy maintenance until day 120.
G. By day 60 the fetus has the unmistakable
appearance of an
equine.
Equine sexing of the embryo can occur around day 62
by noting the position of the genital
tubercle of the embryo.
H. By days 150 to 160 ears will appear fully
developed. Ergots will
appear.
I. By
220 days development of mane and tail have occurred. The
weight of the foal will be about 10
kilograms (22 lbs.)
J. By day 300 the fetus will have a full hair
coat and the weight
will be about 20 kilos (44 lbs.)
K. By 340 days the weight will have reached 45
to 50 kilos (100
lbs.)
We will continue this lesson by
outlining the most important aspects of pregnant mare management as a study
guide and focus for the text reading assignment of chapters 7 and 9.
II. Preventive health care in the pregnant mare.
A.
Regular dental exams and teeth floating.
1. Every 6 months to a year. Schedule to
minimize stress to
mare or fetus.
B.
Regular deworming.
1. Every 3 months. Deworm with Ivermectin within 3 days
of foaling to control Strongoloides
Westeri in foal.
Schedule to minimize stress on mare or
fetus.
C.
Proper nutrition.
1. Best pregnancy rates are achieved in mares in
good to
fleshy body condition. (Condition score of
6 or 7 on 1 to 9
scale.)
2. In the first 2 trimesters mares can be fed a maintenance
ration.
3. In the last trimester the fetus grows 60 to
65 % of its
birthing weight, and therefore, the mare requires
additional calories, protein, Ca, and P
and good quality
vitamins.
D.
Vaccinations.
1. WEE, EEE, VEE,
Scheduled to minimize stress the mare or
fetus.
2. Pneumabort K or
Prodigy at 3rd, 5th, 7th, and 9th
months of pregnancy.
3. Other vaccinations at the recommendation of
your
veterinarian.
4. Vaccination of the mare 1 month prior to
foaling is safe
and recommended to build antibodies in the
colostrums
to transfer to foal. (Flu, Tetanus, and
protection against
sleeping sicknesses is minimal.)
III. Preparing for foaling.
A. One month prior to foaling, vaccinate,
deworm, and move
to future foaling area. Check for caslicks
and open if
necessary; examine udder and abdomen.
B. Within 2 weeks of impending foaling date
begin close
monitoring of perineal area and udder.
C. Within a few days of impending foaling watch
udder
closely, check for relaxing hip and
buttocks muscles and
elongating vulva. Look for waxing and check for
colostrums.
D. Use of Predict-a-Foal kit or a Foal-Watch kit
may be
useful, but is generally not necessary.
Waxing and thick
yellowish orange colostrum normally indicate foaling
within 24 to 48 hours.
IV. Stages of foaling (Parturition)
A. Stage I – restlessness (mild colic signs)
until water
breaks.
1. Usually lasts 20 to 45 minutes.
2. Wrap tail and clean udder and perineal area.
3. Observe
at a distance.
B. Stage II – from breaking of the water to
actual birth of the
foal.
1. Usually lasts from 10 minutes to 30 minutes.
PASSAGE OF FOAL:
2.
One front hoof followed by the second front hoof at
fetlock level followed by the nose at cannon bone
level. If this is not seen within 10 minutes of the
breaking of the water, expert assistance may be
needed.
3.
Once the foal’s head is seen be sure to tear sac
from around the head to allow breathing.
Once the
pelvis passes, allow time before umbilical cord
breaks to allow blood to pass from placenta to foal.
Best to allow for natural breakage of cord.
4.
Disinfect umbilical stump.
5.
Allow for mare and foal to interact and begin
bonding.
C. Stage III –from birth to passage of the
placenta
(afterbirth).
1.
Placenta is normally expelled within 30 minutes to
3 hours of foaling.
retained placenta and veterinary assistance is
necessary to prevent uterine infection and possible
serious complications.
3.
Oxytocin is the drug of choice in retained placenta
to assist in passing the placenta.
V. Induced parturition.
A. The mare must be at full term and show all
signs of
impending foaling.
1.
Musculature relaxation of croup, buttocks and
perineum.
2.
Waxing or milk from the udder.
B. Veterinarian must be involved.
1.
Check for cervix relaxation or dilation.
2.
Check for correct positioning of the foal.
C. Procedure.
1.
The mare is prepared for foaling ( washed and
tail
wrapped).
2.
The mare is given Oxytocin, 3½ cc intramuscularly.
3.
The mare will begin first stage of labor within 10 to
15 minutes and continue through the normal
foaling process.
4.
Induction of parturition can occasionally be
accompanied by complications, so attendance by
veterinarian is crucial.
VI. Events
of the reproductive system of the mare
postpartum.
A. Placental passage is normally within 3 hours
of delivery
of the foal.
B. Day one through 5 will see some bloody
discharges from
the vulva. The uterus will begin to involute.
C. In 8 to
12 days the foal heat will normally occur. (known
as 9-day heat). If mare ovulates after 10 days the chance
of fertility is about the same as
subsequent heats. If
mare is healthy, had no problems foaling
and is
involuting well, breeding is acceptable on
foal heat.
D. 30-day heat usually occurs 25 to 32 days from
foaling.
Uterus is completely involuted back to
pre-pregnancy
condition.
ASSIGNMENT (no quiz)
Please send your answers to the following essay
questions to Dr. Sales at jacksales1234@gmail.com
** Write “Repro Lesson 6 Assignment” in the
subject line of the email. Be sure to include your full name and
email address on all documents.
Please answer each question as completely as possible. I am
looking for an answer that shows me you are knowledgeable about the subject
matter.
1. What procedures are available to diagnose pregnancy in the
mare? Which are most practical?
2. What are endometrial cups and what is their significance?
3. How and by what is pregnancy maintained in the mare?
4. Describe how you would manage the pregnant mares of a breeding
farm from 45 days before due date, through the birthing process. Detail the
three stages of parturition.
5. What is foal heat and what is its significance?
6. Outline a preventive health care program for pregnant mares on
a broodmare farm?