Equine Reproduction
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, West Nile virus, Flu, and
Tetanus. Scheduled to
minimize stress the mare or fetus.
2. Vaccinate during the fifth, seventh, and
ninth months of gestation using an inactivated EHV-1 vaccine licensed for
prevention of abortion.
Many
veterinarians also recommend a dose during the third month of gestation and
some recommend a dose at the time of breeding.
Vaccination
of mares with an inactivated EHV-1/EHV-4 vaccine 4 to 6 weeks before foaling is
commonly practiced to enhance concentrations of colostral
immunoglobulins for transfer to the foal. Maternal antibody passively
transferred to foals from vaccinated mares may decrease the incidence of
respiratory disease in foals, but infection is common in these foals and may
result in clinical disease and establishment of the carrier state.
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.
2.
After 3 hours the placenta is considered to be a
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, 3˝ 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
Please
send to jsales@horsecoursesonline.com "Lesson 6 Repro" in subject
line.
1.
Write a report on how you would manage a pregnant mare starting at 45 days
before the foaling date and up to her foaling.
(Do not include what you would do during foaling and after the foal
arrives – which is covered in lesson 8.)
2. In your own words, briefly name and describe
each stage of parturition.
3.
Explain “foal heat” and in your own words briefly explain why a mare should not
be bred during the foal heat.