Gestation and Parturition Flashcards
What is the average gestation length?
340 days
What is the range of gestation length?
320-365 days (or more)
At what point is the foal viable?
320 days
What factors affect gestation length?
-mare body condition (thin = longer)
-day length (Jan/Feb mares have longer gestation)
-health of mare/foal (health issues may cause early foaling)
-breed/type (ponies have shorter gestation)
-foal sex (gestation with colts is usually longer)
At Day 0 of gestation what occurs?
ovulation, fertilization occurs in the oviduct
At day 6ish of gestation what occurs?
conceptus leaves the oviduct
-it is mobile in the uterus
When is the conceptus detectable in the uterus (with a high powered ultrasound)?
around day 9
At day 16ish of gestation what occurs?
conceptus fixes in a uterine horn
-detectable by ultrasound
At day 23ish of gestation what occurs?
the heart beat is present
-detectable by ultrasound
At day 40 of gestation what occurs (as early as day 35)?
embryo transitions to fetus
-fetal activity and physical development (looks like a horse now)
At day 90ish of gestation what occurs?
placental development is complete
At day 240 of gestation to parturition what occurs?
most fetal mass is accumulated (in the last 3 months)
Early embryonic loss
loss of conceptus prior to 35-40 days (post ovulation)
Abortion
loss of pregnancy between 40 and 310 days (fetus is not viable between these times)
Premature delivery
weak or dead foal pre-term (usually less than 320 days)
Dystocia
a difficult delivery (a full-term dead foal is not considered an abortion)
What are the two sacs of the placenta?
-amnion
-chorioallantois (allantochorion)
Amnion
a white translucent sac of the placenta
-surrounds the fetus
-contains amniotic fluid
Chorioallantois (allantochorion)
a sac of the placenta that surrounds the amnion
-contains allantoic fluid (the “water”)
-has two sides: chorion and allantois
Chorion
the side of the chorioallantois that is attached to the uterus
Allantois
the side of the chorioallantois that is on the side towards the fetus
Umbilical cord
contains blood vessels that transport nutrients and oxygen to the fetus and takes CO2 and some other wastes away
What does the umbilical cord connected to?
the chorioallantois through several tissue layers (keeps the blood cells apart but lets the nutrients/O2 in and the CO2 out)
Do maternal and fetal blood supplies mix?
No
Urachus
connects to the fetal bladder and empties into the allantoic fluid
Where is the urachus found?
in the umbilical cord
Parturition overview:
- the foal breaks through the chorioallantois placenta, allantoic fluid (the water) spills out
- the amnion emerges
- the foal breaks the amnion then emerges
- the placenta is expelled
Pre-partum changes in mares
-loosening of tail muscles (relaxed pelvis)
-elongation of vulva
-udder development
Stage I of parturition lasts how long?
1-3 hours
What occurs during stage 1 of parturition?
-foal changes position
-uterine contractions become more apparent
-mare may be uncomfortable, paw, sweat, roll, etc.
-rupture of the chorioallantois at the end (“water breaking”)
How long does stage 2 of parturition last?
less than 40 minutes (less than 20 minutes is better)
What occurs during stage 2 of parturition?
-begins with the rupture of the chorioallantois (water breaking)
-ends with expulsion of the foal
Steps of stage 2 of parturition:
-chorioallantois ruptures
-amnion should appear first (white)
-one front foot, the other front foot, and then the head of the foal should appear
-rest of the foal comes out
-the umbilical cord should break when the mare or foal stands
Normal foal position during parturition:
diving position
-front foot sole towards mares hocks
-second foot
-nose
-shoulders
-hips
-then hind limbs
Why does one front foot go in front of the other?
to make the shoulders more narrow to fit through the birth canal
How long should stage 3 of parturition last?
less than 3 hours (less than 1 hour is better)
What occurs during stage 3 of parturition?
-ends with the expulsion of placenta
-no expulsion within 3 hours is a retained placenta and an emergency
What should be checked for immediately post-partum with the foal?
-breathing
-righting reflex (sitting up)
-suckle reflex (within about 20 min)
The 1, 2, 3, +3 Rule
- Foal is able to stand within ONE hour
- Foal nurses within TWO hours
- Meconium passed withing THREE hours
+3. Placenta is passed within THREE hours
Meconium
the first manure of the foal
-thick and sticky
-if foal is struggling to defecate, give an enema
What should be done with the umbilical stump?
it should be disinfected 3-4 times/day for 1-3 days with dilute chlorhexidine (Nolvasan)
Early post-partum foal respiration rate:
80 rpm
Foal respiration rate:
30-40 rpm at rest
Foal heart rate:
70-120 bpm
-depending on if they are resting or standing/nursing
Foal temperature:
99.5 to 102 degrees F
What should a foals birth weight be?
9-10% of expected mature weight
What should the placenta weigh?
about 11% of the foal’s birth weight
-very small or very large could indicate a problem during gestation
A foal is born with limited ______ _______
disease protection
Why is a foal born with limited disease protection?
-no transfer of antibodies to pathogens across the placenta
Where are antibodies in the mare concentrated?
in the colostrum (IgG antibodies)
Passive transfer of immunity
what is provided when the foal nursing colostrum off the mare
-the foal is not making the antibodies themselves
When is the best time for the foal to absorb the IgG from colostrum?
0-12 hours after birth
What is going on with the foal’s gut from 0-12 hours after birth?
there is high gut “permeability”
-facilitates absorption of immunoglobulins in colostrum
-other large pathogens can be absorbed now too though (possibly pathogens)
What happens about 12 hours after birth?
“gut closure” begins
-can be earlier in some cases
-harder for foals to absorb large compounds
When does gut closure end?
it is usually complete by at least 24 hours
-too late for colostrum now
Colostrum levels can vary if:
-the mare started dripping colostrum before parturition
-it transitions to milk rapidly
What does a good quality colostrum look like?
gold/yellow, thick, and sticky
You can increase antibodies to common pathogens in colostrum by:
-vaccinating (3 wks - 1 month before the expected foaling date)
-natural exposure to where the mare is foaling, especially if foaling at a different location than where the mare normally lives
If colostrum quality is low what should you do?
give colostrum from the farm’s “bank” or purchase from a commercial colostrum bank (does not have antibodies from your farms environment though)
What is the recommended intake of colostrum?
1-2 liters per foal (about 1/2 a gallon)
How are IgG concentrations assessed?
in foals blood
When should IgG levels be tested?
about 12-24 hours of age (earlier the better so you have time to fix it if its low)
What is low IgG levels a risk of?
it is a risk factor for neonatal disease
-sick foals presented to the clinic have lower Ig levels than healthy foals presented to the clinic
Optimal Ig concentration is:
8-12 g/L
Hyperimmune Plasma
plasma given IV to supplement and increase antibody concentrations if colostrum wasn’t given before 24 hours
Udder scoring system
0 = udder is not producing anything yet, it would appear soft and normal
1 = usually starts about 3 weeks from foaling. There is a small amount of milk production but the udder is still soft
2 = you can feel milk production but the udder is not tight
3 = the udder is tight and full and the teats are pointed outwards
W = wax, the mare is very close to foaling
Foal-alert system
a device that gets sewn into one side of the horse’s vulva. It has a magnet that is sewn into the other side of the vulva and a string connects the two sides. When the string gets disconnected from the magnet, the system will set an alarm off. The alarm is set off when the foals front leg/legs hits the string and disconnects it during stage 2 of labor. It is usually inserted when the mare has an udder score of 3 or no later than her due date if the udder is not developing.
Signs that a pregnant mare is affected by fescue toxicosis
-prolonged gestation
-little to no mammary gland development (even close to foaling)
Why is examining the placenta after foaling important?
it can tell you of any complications during pregnancy and more about the issues a mare possibly had during pregnancy that could be a problem for her foal. Also if part of the placenta is retained, that is an emergency and the mare is at severe risk of infection and must get vet care
Where does the chorioallantois usually rupture during foaling?
at the cervical star
Hippomane (allantoic calculi)
an oval mass that is tan or brown in color and is passed along with the placenta
-it is an aggregate of cells, lipids, and debris that can accumulate during normal gestation
Foaling kit
a kit prepared at the beginning of the season before the first foal is due
-gloves
-flashlight
-stethoscope
-scissors/suture scissors
-umbilical dip cups and colostrum sample cups
-bottle
-enemas
-bailing twine (to tie placenta)
-brown gauze (to wrap mares tail)
-towels
When is the udder score determined?
in the morning
-in the afternoon udders can go down with movement/exercise throughout the day
Refractometer
used to test colostrum quality
-0-30
What number on the refractometer tells you it is poor quality and colostrum from the bank should be used?
anything less than 21
Pregnant horn appearance?
thicker, fuller, larger
Non-pregnant horn appearance
shriveled, smaller
Chorion appearance
red, velcro-like, veiny
Allantois appearance
soft, velvet-like (inside of placenta)
Red bag
premature separation of the placenta
-the cervical star did not tear so you see the red chorionic surface first
-EMERGENCY, foal is not getting enough oxygen
Characteristics of the placenta that is evaluated:
-color (no discoloration spots)
-both horns are intact
-look for tears
-weight
