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Gestation and Foaling


Mares with fillies foal on average 3 d earlier. Gestation Length ... is through the vulva the foal can breathe on its own. ... Foal must receive within 1st 8 ... – PowerPoint PPT presentation

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Title: Gestation and Foaling

Gestation and Foaling
Gestation Length
  • 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

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

Equine Gestation HormonesProgesterone/Progestogen
  • 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
  • Second ? associated with formation of accessory
    secondary CL. 
  • The 5 a pregnanes rise from mid gestation to
  • Produced from maternal cholesterol
  • Late gestation progestagen rises (last month of

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.

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
  • 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.

  • Placenta takes over progestagen production d 100
    until foaling.
  • Complete placental formation is done at 150 days.

DAY 150 - Firm placental attachment
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Impending Birth
  • Vaccinate Deworm 30 day prior
  • Most Obvious
  • Hypertrophy mammary glands obvious from 8th month
  • Maiden may display little until just before
  • 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

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Impending Birth
  • More Subtle Signs
  • Softening and flattening of the muscles in the
  • Vulva becomes relaxed elongated. Maximal hours
    before parturition
  • Visible changes in the position of the foal
  • Vulva thick puffy with edema and may elongate

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

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

  • 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

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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
Stages of Parturition
  • Stage 3
  • Onset delivery of fetus
  • End passage of the fetal membranes
  • Expel placenta 1- 3 hrs post-foaling
  • Examine Placenta

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
  • Allantoamnion - allantois surrounds the amnion by
    the 4th week of gestation, forming the
  • At term, this membrane is white and opaque, with
    large blood vessels coursing over the inner
  • 1/3 of weight at term

Fetus _at_ 3 months
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

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.
Placenta Examination
  • 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

  • Usually expelled with the allantoic surface
  • 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
  • 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.

  • 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

Chronic Inflammation Cervical Star
  • 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
  • Allantoamnion
  • assessed for uniform thickness and color
  • smooth, white, opaque, uniformly thin membrane.

  • 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

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

Premature seperation
Ascending placentitis
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

  • First milk secreted by a mare coming into
  • Production
  • During last 2-4 weeks of gestation
  • Under hormonal influences
  • Importance
  • 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

  • Quality
  • Relates directly to antibody content
  • Good quality
  • 50 (70) g/L IgG and specific gravity gt 1.060
  • Thick, sticky, yellow secretion

  • Quality
  • Decreased quality
  • Maiden mares and mares gt 15 y of age
  • Certain breeds (Standardbred)
  • Shorter gestation (early foals)
  • Sick mares
  • Poor foaling conditions

  • Evaluating Colostrum Quality
  • Colostrometer
  • Measures specific gravity/density
  • of colostrum
  • Approx. 6 ml of colostrum needed
  • Specific gravity gt1.060 indicates good quality

  • Evaluating Colostrum Quality
  • ARS Refractometer
  • Designed for measurement of sugar concentration
  • solutions (BRIX type)
  • 1-2 drops of colostrum needed
  • Results in less than 1 minute
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Evaluating Colostrum Quality
ARS Refractometer - Results
  • Volume
  • Average total volume 5 liters (3.2-7.0 l)
  • Primiparous lt multiparous mares
  • Decreased in stressed, injured or ill mares
  • Decreased in mares with mastitis or other damage
    to udder

  • Evaluating Colostrum Quality
  • When?
  • Assess before foal suckles
  • How?
  • Physical appearance
  • Thick, sticky, yellow secretion indicates good
  • 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

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-
  • 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

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

Foal Immune Status
  • What are safe levels of IgG in the foal?
  • True safe levels not known
  • Goal serum IgG gt 800 mg/dl
  • If lt 800 mg/dl Failure of
  • Passive Transfer (FPT) - As high as 20 of all
  • Marginal FPT IgG 400-800 mg/dl
  • Partial FPT IgG 200-400 mg/dl
  • Complete FPT IgG lt 200 mg/dl

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
  • Can measure early at 6-12 h
  • IgG first detected in foals serum at 6 h of age
  • If no IgG or very low level at 6-12 h can give
    colostrum to increase levels

Foal Immune Status
  • Evaluation of serum IgG status
  • Snap Foal IgG Test
  • 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
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