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Gestation and Foaling

Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

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Page 1: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Gestation and Foaling

Page 2: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

• Average 338-343 days.

• Normal gestation can range from 320-380 days.

Gestation Length

Page 3: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

• Gestation length shorter in TB and SB (325-340) than Draft mares (350-375d)

• Mares bred in late winter & early spring have gestation lengths that average 10 d longer then those born in summer.

• Mares with fillies foal on average 3 d earlier

Gestation Length

Page 4: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Early Embryo

• 5-6 days enters uterus• Migrates to day 16.

– Embryo migrates in the uterus for ~ 16 days to release a 'signal' that pregnancy is established.

– Fixation of the embryo (gestational sac) occurs at ~ 16 days post ovulation

Page 5: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Equine Gestation HormonesProgesterone/Progestogens

• Progesterone initially rises, followed by a slight ↓ then ↑ to a peak at d 80, then gradually ↓ to 1-2 ng/ml during mid-late gestation (d 150). 

• Second ↑ associated with formation of accessory & secondary CL.  • The 5 α pregnanes rise from mid gestation to term. 

– Produced from maternal cholesterol • Late gestation progestagen rises (last month of pregnancy)

Page 6: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Equine Gestation HormonesEstrogens

• Mare ovarian estrogens begin to ↑ at d 38-40.   – From gonadotropin stimulation of luteal tissue – Late in gestation maternal estrogen production ↑.

• D 70-80 a 2nd ↑ of estrogens from the fetal-placental unit occurs.   – Secreted by fetal gonads.

• Fetal estrogens peak at about 210 d & decline & are basal • Estrogens appear in the mare's urine in large amounts in the latter half of

gestation. – Estrone sulfate: Can be measured with a kit. Derived from the placenta, it is an

indicator of fetal viability. It declines within a few days of fetal death.

Page 7: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Equine Gestation HormonesEquine Chorionic Gonadotropin (eCG)

• 36-38 days - fetal tissue along the chorionic girdle begin to invade the endometrium & form the endometrial cups.  

• Endometrial cups - eCG-Equine Chorionic Gonadotropin • Produced ~ d 37-42, • Peak - d 60-80• Endometrial cups start to decline, disappearing around d 120-150.  • Causes luteinization of follicular waves to create secondary CLs. • Has an FSH-like action in many other species, it has LH-like activity

in mares.

Page 8: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Placenta

• Placenta takes over progestagen production ~d 100 until foaling.

• Complete placental formation is done at 150 days.

DAY 150 - Firm placental attachment

Page 9: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length
Page 10: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Impending BirthVaccinate & Deworm 30

day priorMost Obvious• Hypertrophy mammary

glands obvious from 8th month– Maiden may display little

until just before foaling• Distention of the teats

4-6 d pre-foaling • Waxing of the teats

1-72 hrs pre-foaling• An increase in milk Ca

1-3 d pre-foaling

Page 11: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length
Page 12: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Impending BirthMore Subtle Signs

• Softening and flattening of the muscles in the croup

• Vulva becomes relaxed & elongated. Maximal hours before parturition

• Visible changes in the position of the foal

• Vulva – thick & puffy with edema and may elongate

Page 13: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Stages of Parturition

• Stage 1– Onset: initial uterine

contractions– End: rupture of

chorioallantois (water bag)

– 1-2 hr– Mare may stand up, lie

down, roll, pace, look or bite at flanks, sweat, urinate

Page 14: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Stages of Parturition

• Stage 2– Onset: rupture of

chorioallantois– End: delivery of fetus– Timeline 30 min– Contractions occur in

groups of 3-4 followed by a rest period of 3 to 5 minutes

Page 15: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

• When the chest is through the vulva the foal can breathe on its own. May go in & remove the amniotic sac.

• Not breathing – rub foal, take straw and put in nose, breath into nose

Page 16: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length
Page 17: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length
Page 18: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Foaling EmergenciesMay Need Assistance

• Red mass evident at vulva (placenta seperation)

• Strong straining & no feet evident at vulva within 5 min

• Heavy straining with feet in vulva but no further progress in 10 min

• One foot missing• No progress for more than 15 min

after first water breaks• Rectovaginal perforation occurs• Mare foals while standing

“Red Bag”

Page 19: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Stages of Parturition• Stage 3

– Onset: delivery of fetus– End: passage of the fetal

membranes– Expel placenta 1- 3 hrs

post-foaling•Examine Placenta

Page 20: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Fetal Membranes at Parturition • Allantochorion - Fusion of the allantois with the chorion results in the

allatochorion. At term ~2/3 of placental weight. – Chorionic (villous) surface is intimately applied to the maternal

endometrium and is responsible for the formation of microcotyledonary attachments. Grossly, it appears as a red velvet surface

• Allantoamnion - allantois surrounds the amnion by the 4th week of gestation, forming the allantoamnion. – At term, this membrane is white and opaque, with large blood

vessels coursing over the inner surface.– 1/3 of weight at term

Fetus @ 3 months

Page 21: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Fetal Membranes at Parturition • Umbilical cord - Results from the expansion of

the amnion & allantois around the remnants of the yolk sac & vitelline duct – Anchors the fetus to the original implantation site at the

base of the gravid horn on the dorsal wall of the uterus.– Cord length is directly correlated with the weight of the

allantoamnion and the allantochorion.

Page 22: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Important Features of the Equine Placenta

• Cervical star visible as a region without the red villi and has radiating, bare, white areas from its center

• Allantochorionic Pouches - Maternal rejection of the endometrial cups results in their sloughing into adjacent invaginations of the overlying allantochorion. These appear as pedunculated structures forming a ring around the site of umbilical cord attachment at the dorsal wall of the pregnant horn.

• Hippomanes are yellowish/green pasty concentration products of fetal urine and contain large numbers of birefringent crystals

Placental with fetus showing the "cervical star", site of future rupture of membranes.

Page 23: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

•Arrange the membranes in a capital "F" position, with the pregnant horn uppermost and the body forming the vertical bar of the "F"•Tip of the nonpregnant horn is the most likely part of the placenta to be retained•Placenta Examination

•Weight •Length of umbilical cord & location•Appearance of gross lesions, missing pieces

Placenta Examination

Page 24: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Allantochorion• Usually expelled with the allantoic surface outermost• Examine both chorionic and allantoic surfaces.• Color

– Rich red or maroon color with the gross appearance of a velvet-like surface.– Pale or fibrotic areas indicate sites of placental detachment or lack of

microcotyledon formation– Nonpregnant horn is generally paler than the rest of the chorion.

• Thickness– Compared with the pregnant horn, the non-pregnant horn is thinner in section,

puckered, and smaller in size.

Page 25: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Allantochorion• Body Pregnancy

– Although usually resident in one uterine horn with extension into the body of the uterus, the occasional fetus will develop largely within the body of the uterus. The characteristic placental finding is short, symmetrical placental horns

• Exudate– Presence may be considered as presumptive evidence of microbial

intrauterine infection

Page 26: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Allantochorion

• Cervical Star Thickening

– majority of Intrauterine infections ascend through an incompetent cervix.

– Gross thickening, exudate, and a line of demarcation between this area and the adjacent placental body are characteristic findings of placentitis

• Allantoamnion

– assessed for uniform thickness and color

– smooth, white, opaque, uniformly thin membrane.

Chronic Inflammation Cervical Star

Page 27: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Allantochorion

• Umbilical Cord– Assessment of length, degree of twisting, and the

presence of any vascular compromise– Abnormal findings include cord seperation, excessive

rotation, kinking, aneurysms, intramural hematomas, thrombosis, edema

– 95% of normal equine pregnancies, the umbilical cord measures between 36 and 83 cm, with an average length of 55 cm

Page 28: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Postpartum Mare & Foal Care

Umbilical Cord Care • Allow foal to break fetal membranes.• Never cut the cord.• Spray umbilical cord stump with antiseptic

solution 3-4X per day for 3-4 days

Ascending placentitis Premature seperation

Page 29: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Retained Placenta: Treatment

• After 2 hrs

• Oxytocin

• Infusion of fluid into allantoic cavity

• Antibiotics

• Non-sterioidal anti-inflammatory drugs

• Frog support pads

• Deeply bedded stall

Page 30: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum • First milk secreted by a mare coming into

lactationProduction• During last 2-4 weeks of gestation• Under hormonal influencesImportance

• Transfer of passive immunity to the suckling foal (“Liquid Gold”) Specificity of protection achieved by vaccinating pregnant mares 30-60 days before parturition

• Produced only once – beware of leakage!

• Provides energy to foal

• Encourages passage of meconium

Page 31: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum Quality• Relates directly to antibody content

• Good quality: ≥ 50 (70) g/L IgG and specific gravity > 1.060

Thick, sticky, yellow secretion

Page 32: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum

Quality• Decreased quality:

Maiden mares and mares > 15 y of age

Certain breeds (Standardbred)

Shorter gestation (early foals)

Sick mares

Poor foaling conditions

Page 33: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum

Evaluating Colostrum Quality

Colostrometer

• Measures specific gravity/density

of colostrum

• Approx. 6 ml of colostrum needed

• Specific gravity >1.060 indicates

good quality

Page 34: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum

Evaluating Colostrum Quality

ARS Refractometer

• Designed for measurement of sugar

concentration of

solutions (BRIX type)

• 1-2 drops of colostrum needed

• Results in less than 1 minute

http://www.arssales.com/equine/html/refractometer.html

Page 35: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum

ARS Refractometer - Results

Evaluating Colostrum Quality

Page 36: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum

Volume• Average total volume: 5 liters

(3.2-7.0 l)

• Primiparous < multiparous

mares

• Decreased in stressed,

injured or ill mares

• Decreased in mares with

mastitis or other damage to

udder

Page 37: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Colostrum Evaluating Colostrum QualityWhen?• Assess before foal sucklesHow?• Physical appearance

Thick, sticky, yellow secretion indicates good quality Dilute, white or translucent secretion indicates poor quality

Stall Side Tests

Banking of Colostrum

• Only good quality colostrum

• Storage at -20ºC:

– IgG concentration stable for 12 months

– Other immune components (complement, etc) and

nutritional components decrease significantly

• Storage at -70ºC:

– Permanent maintenance of all components

Page 38: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Passive Transfer• Successful passive transfer depends on precise sequence of

events– Antibodies must be present in colostrum– GI tract must absorb the large proteins whole- “pinocytosis”

• Foal must receive within 1st 8-12 hrs of life• Requires 8-12 hours for antibodies to show up in the blood• Uptake declines to almost zero by 12-24 hours

Page 39: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Antibody levels in Foal

0

200

400

600

800

1000

1200

1wk

2wk

3wk

4wk

5wk

6wk

7wk

8wk

9wk

10wk

11wk

12wk

Mare IgG

Foal IgG

•Foal produced antibodies first appear in blood stream at about 3 Foal produced antibodies first appear in blood stream at about 3 weeks of ageweeks of age•Normal adult levels of foal produced antibodies by 4-5 monthsNormal adult levels of foal produced antibodies by 4-5 months

Page 40: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Foal Immune Status

What are safe levels of IgG in the foal?

• True safe levels not known

• Goal: serum IgG > 800 mg/dl

• If < 800 mg/dl = Failure of

Passive Transfer (FPT) - As high as 20% of all foals

Marginal FPT: IgG 400-800 mg/dl

Partial FPT: IgG 200-400 mg/dl

Complete FPT: IgG < 200 mg/dl

Page 41: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Foal Immune Status Evaluation of serum IgG status

When? Typically at 12-24 h after birth

Peak serum levels of IgG achieved by 18h Absorption of immunoglobulins from small intestine

essentially complete If failure of passive transfer: treat with IV plasma

Can measure early at 6-12 h IgG first detected in foal’s serum at 6 h of age If no IgG or very low level at 6-12 h: can give colostrum to

increase levels

Page 42: Gestation and Foaling. Average 338-343 days. Normal gestation can range from 320-380 days. Gestation Length

Foal Immune Status Evaluation of serum IgG statusSnap Foal IgG Test• ELISA

• Use whole blood, serum, or plasma

• Calibrator spots indicate IgG

levels of 400 and 800 mg/dl

• Sample color is proportional to

IgG content

• Results in 10-15 min.

• Expensive but convenient