Equine Pregnancy
103-153, 157-165, 177-178

Physiology of Pregnancy

The Early Embryo

  • At about 24 hours post ovulation the embyro is at 2 cell stage

  • 4-5 days - morula

  • 5-6 days blastocyst

  • 5-6 days enters uterus and zona shed

  • Capsule forms at blastocyst stage

    • Protective covering

    • Origin not clearly known - may be embryonic, may have endometrial contribution

    • Lost at 21 days


  • Migration to day 16. The embryo migrates in the uterus for approximately 16 days to release a 'signal' that pregnancy is established. Fixation of the embryo (gestational sac) occurs at about 16 days post ovulation.



Endometrial cups

  • At about 36-38 days, fetal tissue along the chorionic girdle begin to invade the endometrium and form the endometrial cups.  

  • Endometrial cups secrete eCG ...Equine Chorionic Gonadotrophin (formerly PMSG...Pregnant Mare Serum Gonadotrophin). This acts to luteinize the normal follicular waves that are occurring and results in formation of the secondary corpora lutea.  

  • The cups remain, even if the pregnancy is lost, and are then sloughed at the normal time (120 days).

Equine chorionic gonadotropin (eCG): (formerly pregnant mare serum gonadotropin or PMSG)

  • Produced by the endometrial cups beginning around d 37-42, peaking around d 60-80, after which the endometrial cups start to decline, disappearing around d 120-150. 
  • The function of the endometrial cups and eCG are unclear. 
  • Some hypothesize an immunologic role in helping to maintain pregnancy.
  • Causes luteinization of follicular waves to create secondary CLs.
  • Although eCG has an FSH-like action in many other species, it has LH-like activity in mares.

Secondary CLs

  • The secondary CLs result in progesterone rise about day 60-120. The endometrial cups regress (they are sloughed from the uterus by an immunologic response).  
  • Secondary vs. accessory CLs (ovulatory or anovulatory)


  • Progesterone initially rises, followed by a slight decrease then rises to a peak at d 80, then gradually declining to 1-2 ng/ml during mid-late gestation (d 150). 
  • The second rise is associated with the formation of accessory and secondary CL. 
  • The 5 alpha pregnanes rise from mid gestation to term. 
    • Produced from maternal cholesterol
  • The fetoplacental unit produces sufficient progestagens so that ovariectomy can be performed after 120-150 d.
  • Late gestation progestagen rises (last month of pregnancy)
    • From fetal adrenal  production of 5 alpha reduced pregnanes (adrenals do not have 17 alpha hydroxylase)



  • Mare ovarian estrogens begin to rise at day 38-40.  
    • From gonadotrophic stimulation of luteal tissue
    • Late in gestation maternal estrogen production rises.
  • At day 70-80 a second rise of estrogens from the fetal-placental unit occurs.  
    • Placental aromatization of the common C-19 precursors
    •  dehydroandrosterone (DHA) and dehydroepiandrosterone (DHEA)
    • Secreted by fetal gonads.
  • Fetal estrogens peak at about 210 days and decline and are basal at term. 


  • The placenta takes over progestagen (not progesterone) production until foaling. Therefore, a mare does not need her ovaries after about 120 days of gestation.
  • The mare has diffuse type of microcotyledonary placenta
  • Complete placental formation is done at 150 days.

Equine Placentation adopted from Ginther

Day 9-10 

Inner cell mass (brown) 

Yolk sac starting 

Day 14

Still mobile

Mesoderm will be blood vessels and  connective tissue.


Day 16 

Folds start to form over embryonic disc to form amnion. 

Day 48-19

Amnion has formed.

Note the two and three layered areas.


Day 21

Allantois is emerging. 

Day 25

Allantois has moved over embyro.

Heart beat present.

Note red developing chorionic girdle. 

Day 30

Note red chorionic girdle which will form the endometrial cups.

Day 40

Embryo moved to opposite pole. 

Yolk sac replaced by allantois.

Day 80

The yolk sac is only a remnant.

Conceptus fills both horns.

Pregnancy Diagnosis

  • Certain characteristics of pregnancy in the mare aid in diagnosis. 
  • Progesterone causes increased tone of the uterus and cervix. 
  • Estrogen from the conceptus, in conjunction with the progesterone results in exaggerated tone. 
  • The vesicle is spherical and distinct, and can be palpated from 18 d (+) through 60-70 d, and seen with ultrasound beginning at 10 or 12 d (depending on the machine).


  • Other significant characteristics of equine pregnancy include the presence of chorionic girdle cells from the fetal trophoblast which invade the endometrium. The ovaries are active during pregnancy, with large follicles palpable especially around 18-23 d and 36-45 d.




  • Estrogens are primarily from the fetal gonads in late pregnancy. 
  • The fetal gonads increase in size and are larger than the maternal gonads at 8 mos. gestation, decreasing in size after 300 d. 
  • Estrogens appear in the mare's urine in large amounts in the latter half of gestation.  
  • Estrone sulfate: Derived from the placenta, it is an indicator of fetal viability. It declines within a few days of fetal death.




Click on the BET labs icon to see their web page and find out what hormones they run.

External signs of pregnancy  

  • Although abdominal enlargement is characteristic of pregnancy, it is unreliable as a diagnostic sign. 
  • Ballotment or observed movements of the fetus can often be seen late in gestation. 
  • Mammary changes are quite variable. 
  • Pelvic changes (relaxation of the pelvic ligaments) occur late in gestation but are often difficult to detect. 
  • Cessation of estrus behavior is variable and unreliable. 
    • Some mares will continue to show estrus even when pregnant.

Methods of diagnosis
Palpation per rectum  
  • Cervical changes from 16 or 17 d to term are elongation, firmness and tubularity. The uterus also has increased tone.
  • The chorionic vesicle is distinct and spherical and approximate sizes are:  
    • 28 d (4 wks) Key lime (pullet egg)  
    • 35 d (5 wks) lemon  
    • 42 d (6 wks) orange  
    • 49 d (7 wks) grapefruit  
    • 56 d (8 wks) cantaloupe  
    • By 90 d it is hard to delineate the cranial margin of uterus.  
    • Fetal Ballotment per rectum becomes consistent after 150d.  
    • Aging fetus by size, as in the cow, is imprecise.  
    • Differentials which may confuse the examiner include the bladder and enlargement in the non pregnant tract at the base of the uterine horn.


  • The time of earliest diagnosis depends on the MHZ of the probe. 
  • Gestational age can be estimated from the size of the vesicle. 
  • There is a plateau in the growth curve between d 17-24 during which the size does not increase much.

  • Movement of the vesicle is characteristic of early pregnancy, covering the entire uterus and moving surprisingly rapidly. 
  • Movement ceases around d 16-17 when "fixation" occurs.

    Movement of the equine embryo.
  • The fetal heartbeat can be observed around d 23-24.
  • The vesicle undergoes a series of changes, having a very characteristic appearance at various stages with which the examiner should be familiar. 
  • The vesicle usually becomes fixed in a location at the base of a uterine horn. 
  • Although initially spherical, the shape becomes more triangular around d 18 and the embryo becomes visible around d 20-21, usually in a ventral location. 
  • Changes in the shape of the vesicle and the characteristic location of the embryo are related to the developing trophoblast. 
  • At d 21, the embryo is at the bottom of vesicle and the entire hypoechoic structure is the yolk sac. 
  • Soon thereafter the developing allantoic membrane can be seen. 
  • By d 30 the embryo is found in the middle of the vesicle suspended by the developing allantoic membrane, with the allantoic sac beneath and the yolk sac above. 
  • By d 36 the embryo is near the top of the vesicle and the yolk sac is all but gone. 
  • By d 40 the embryo is back in the middle of the vesicle, suspended by the umbilicus. 
  • Vesicles that are smaller than normal size for their age are associated with increased rates of embryonic loss. 
  • One of the critical reasons for a thorough early pregnancy exam is to detect twins, which will be discussed in more detail later.

    Fetal sexing

    • Fetal sexing is becoming more and more in demand. 
    • Numerous reasons exist for owners desiring knowledge of the sex of the fetus, such as appraisals, insurance coverage, payment of stud fees, sales consignments, mating lists, sale or purchase, etc. 
    • The veterinarian performing fetal sexing should be aware of the liability implications involved. 
    • Gender determination is based on the location of the genital tubercle. 
      • The genital tubercle is the precursor of the penis in the male or the clitoris in the female. 
      • The tubercle migrates toward the umbilicus in the male and toward the anus in the female. 
    • Ideal times for performing the procedure are from 59 to 68 days or 5 to 6 months. 
      • Before 58 days the tubercle is not distinct enough and has not migrated sufficiently to make a distinction. 
      • After 70 days the fetus is hard to reach until it is approximately 3.5 to 4 months of age. 
      • As the fetus gets larger, a trans-abdominal approach may be preferred. 
    • It is important to mention that accuracy is based on certainty and that the veterinarian should keep their own written records. If cattle are available, it is easier to learn the technique on cattle because the manipulations are easier and they are more tolerant of prolonged rectal examinations.

    Indirect pregnancy tests  

  • The presence of eCG has been used as a test for pregnancy because it is only found in pregnant mares. 
    • The problem is that it remains elevated after the cups are formed even if fetal death occurs. In house tests are available which makes them attractive in some situations (e.g. miniature horses). 
    • For example, with the Synbiotics test, it is reported that 20% of samples are positive at 30 d, 66% at 38 d, 76% at 40 d, and 92% at 42 d.

      Endometrial cups in a mare.
  • Estrogens are elevated 150 d to term (due to production from fetal gonads). 
    • The Cuboni test, based on fluorescence of urine, is 90% accurate after 100 d, 100% accurate after 150 d. 
    • Generally, that late in gestation, other means of pregnancy diagnosis have already been employed.

      Cuboni test.
  • Estrone sulfate can be tested for in almost any bodily fluid. In serum there is a sharp rise after 60 d, peak levels by 80 d. 
    • Before 60 d a false positive can be obtained due to estrus. In milk a similar pattern is observed, only with lower values. 
    • It is considered an indicator of fetal viability after 44 d. In feces, it can be found after 4 mos. And can also be found in urine. Testing is noninvasive and therefore used in studies of wild equids.
    • Commercial tests available "Equi Test - ES" (www.trideltaltd.com); "Confirm" (http://www.icpbio.com/site.aspx/Pages/Products/ConfirmEquine)
Early Pregnancy Factor
Check this link out to a potentially exciting method to determine  pregnancy.
  • EPF - two components
    • EPF-A - Uterine tube 
    • EPF -B - Ovary
    • Production requires signal from fertilized ovum (ovum factor) released under prolactin presence after sperm penetration. 
    • Appears 4-6 hours
    • Disappears with fetal death
    • Non-detectable at 20 days in milk and 30 days in serum
    • Lateral flow dipstick test
    • It does not work in the cow, so I have doubts in the mare.
    • I have seen no refereed papers about its use in the mare.

Problems of Pregnancy 

Uterine torsion  

  • Uterine torsion is an uncommon problem, found usually late in gestation (7 mo to term) but not usually at parturition (unlike the cow). 
  • It is thought that the reduced incidence in the mare can be attributed at least in part to anatomical differences from the cow in the attachments of the uterus to the body wall by the broad ligament and to the method of rising (front end first as opposed to cow). 
  • The clinical signs are those of colic.
  • Diagnosis is made by rectal palpation. 
    • The broad ligaments are crossed, one going over the uterus, the other below. 
    • The location of the ovaries is abnormal as well. 
  • A vaginal exam is usually not very helpful, as the vagina and cervix are rarely involved. 
  • Treatment is generally surgical via either a standing flank laparotomy or midline laparotomy. 
  • After correction, the pregnancy is allowed to continue to term. 
  • Rolling has also been reported (JAVMA 193:3, p337). 
    • In that report, 6 of 7 were successfully corrected, with 1 uterine rupture (355 d gestation, previous attempt at correction).

Prepubic tendon rupture 

  • More commonly seen in older, heavier (draft) mares, it is not common in athletic breeds. 
  • There is probably not really an actual pre-pubic tendon. It is really a tear in the muscle.
  • The first sign is ventral edema. 
  • This is followed by a "Dropped" abdomen. 

  • The mammary secretions may become bloody. 

  • Treatment consists of abdominal support and reducing activity. Parturition or induced or assisted or an elective C-section has been the traditional treatment. A report from U Penn (JAVMA 232:257-261, 2008) indicates that a conservative approach (wait and let the mare foal) may result in better mare and foal prognosis.
  • The prognosis is poor for survival of both the dam and the fetus.

  • Normally parturition occurs at night, and the mare seemingly can delay parturition until the setting suits her. 
  • Horses have a very variable gestation length (ave 335, range 305-405). 
  • It is a very rapid process. Often being completed in less than 20 min.

Signs of impending parturition in the mare  

  • Udder development is evident 3 to 6 wks prior to foaling. 
  • "Waxing" or the presence of a very thick drop of sticky colostrum at the teat end, can be observed 1-72 h prior to parturition. 

  • Some mares may leak colostrum for days, to the extent that insufficient good quality colostrum is available when the foal is born. 
  • There is slight relaxation of the sacrosciatic ligaments but this is not as evident as in cows, especially in the heavily muscled breeds like Quarter Horses. 
  • The vulva becomes edematous and lengthens. 
  • Most importantly, there is a change in the electrolytes in the mammary secretions. 
    • Sodium decreases, 

    • Potassium and magnesium increase, 

  • Calcium increases sharply. 

  • A point system based on these changes was developed by Ousey et al. to aid in predicting foaling. Others watch for the crossing of the sodium and potassium curves in addition to elevated calcium.








> 10

< 30

> 35


> 7

< 50

> 30


> 5

< 80

> 20



  • The most important change is an increase in divalent cations (Ca++, Mg++) in milk. 
  • The increase in magnesium is more gradual and occurs earlier pre-partum than Ca++.  It is the increase in Ca++ that is most useful. 
  • When calcium rises >10 mmol or 400 ppm, parturition is imminent.

Characteristics of parturition in mares  

  • Stage 1 is characterized by restlessness, walking, frequent urination, sweating, the mare is anxious, looking at her abdomen, getting up and laying down, rolling. 
    • Most mares will rise at least once after going down, but repeatedly getting up and down may signal a problem. 
    • The foal has an active role in its final positioning, going from dorso-pubic to dorso-sacral. 
    • The duration of Stage 1 is usually about an hour or a little longer (10 min - 5.5 h). 
    • Stage 1 ends with the rupture of the chorio-allantois at the cervical star.  
  • Stage 2 consists of 15 to 30 min of very forceful expulsive efforts. 
    • The foal is presented in the intact amnion, usually with one forelimb about 6 in. behind the other. 
    • The long umbilical cord remains intact until the mare rises. 
    • It was once thought that significant blood flow, up to 1 liter, occurred through the cord after birth and people were cautioned about breaking the cord too soon. 
    • However, more recent studies have shown that there is no significant blood flow in the cord after birth and there is no difference in the PCV between foals in which the cord is broken soon after birth and those in which the cord is left intact.  
  • Stage 3 typically appears as a tranquilizing effect post-delivery. 
    • The placenta is usually passed in less than 3 h after parturition. 
    • After delivery, the navel should be disinfected with 2% chlorhexidine. 
    • Non-tamed iodine is associated with an increased incidence of patent urachus, and other problems because it is too harsh. 
    • Povidone iodine does not disinfect adequately.  
    • Good colostrum has a specific gravity >1.06 and adequate intake should be observed. Inspection of the placenta should be routine. 
    • Make sure that all the placenta has been passed. 
    • Check for signs of placentitis. Any abnormal areas may indicate septicemia of the foal. 
    • Treatment should begin immediately, before clinical signs appear in the foal. Also check for other abnormalities in the placenta. Areas of aplastic or hypoplastic villi are an indication of uterine pathology.  


  • Considerations to keep in mind in the management of dystocia are that the process of parturition is very rapid and very forceful. 
  • The reproductive tract of the mare is easily traumatized. Mares can be unpredictable during dystocia and it is advisable to use caution.


Guidelines on when to intervene:  

  • After 10 min of strenuous labor and no sign of the fetus perform an examination. 
  • If the forefeet and muzzle are in the canal, allow the mare to continue. 
  • After strenuous contractions for another 10 min, assist delivery. 
  • The amnion, which is a white membrane, should protrude from the vulva within 5 min of rupture of the chorio-allantois. 
  • If a red velvety membrane (the chorio-allantois) is seen at the vulva, a true emergency exists.  This is termed 'red bag'.
  • Unfortunately, if intervention is needed, oftentimes the foal will be dead. 
  • Assistance must be given rapidly if the foal is to be saved. 
  • A weak or dead foal cannot assist in the process of parturition.

Proper restraint, both physical and chemical are important.  

  • Minimize the use of drugs that will affect the CNS and cause respiratory depression of the foal. 
  • For sedation or tranquilization, acepromazine is not recommended if the foal is alive because of its long clearance time. 
  • Barbiturates are also not recommended because of severe fetal depression, even with doses that don't affect the mare. 
  • Both xylazine and detomidine can be reversed with yohimbine (0.05 mg/lb, IV). 
    • Caution should be exercised if xylazine is used alone as it will sometimes result in hypersensitivity of the hindquarters. 
  • Epidural anesthesia is not recommended because it takes too long to take effect, doesn't stop the abdominal press and may cause the mare to be unstable in the hindquarters if she ends up needing to be shipped somewhere or during recovery if she undergoes general anesthesia.  
  • Short term field anesthesia can be accomplished with xylazine (1 mg/kg IV) or detomidine (10 g/lb, IV) followed by ketamine (2 mg/kg IV) after the mare drops her head. Then administer "triple drip": 5% glycerol guaiacolate (GG) solution containing 0.5 mg/ml xylazine (or 20 g/ml detomidine) plus 1 mg/ml ketamine administered at approximately 1.0 ml/lb/hr (if give a second bag use 0.25 mg/ml of xylazine).  
  • If the foal is dead, you can use glycerol guaiacolate and thiobarbiturate.  
  • For Caesarian section: give GG (5% Sol.) to effect, then ketamine (1mg/lb) then intubate (Isoflurane preferred over Halothane); if pre-medication is desired, 50 mg valium can be given IM, 10 mg butorphanol IV.  
  • After delivery, give the foal Dopram (0.2 mg/kg, IV) and yohimbine if needed.

Cleanliness and lubrication are absolutely essential in the management of equine dystocia.

  • Petroleum jelly is a good choice of lubricant. 
  • Water soluble lubricants are acceptable but must be replenished more often. 
  • Do not use a detergent as a lubricant because it has a de-fatting action on the tissues.
  • Do not use J-lube, particularly if a C-section may be anticipated. J-lube has been found to be quite toxic if in the peritoneum.

Prompt assessment of the cause of dystocia is important as is relatively rapid decision making as to the course of action.

  • Abnormal fetal posture is the most common cause of dystocia because of the long extremities and neck of the foal. 
  • Normally, the foal is an active participant in parturition. 
  • A weak or dead foal fails to participate in the process. 
  • Congenital deformities such as wry neck, contracted tendons or ankylosis result in dystocia. 
  • Dog sitting posture, foot-nape presentation (often causing a recto-vaginal laceration if not corrected) and nape presentation are fairly common problems. 
  • Abnormal presentation, e.g. posterior or ventral-transverse also may be encountered. 
  • Twins frequently result in dystocia. 
  • Maternal causes, such as a tight vaginal-vestibular sphincter, a small vulva or Caslick's that was not opened may also be involved.

Premature separation of the chorio-allantois (or "red bag" in lay terms) is an obstetrical emergency. 

  • This can be recognized by the appearance of a red, velvety membrane at the vulva before delivery of the foal. 

  • The chorio-allantois must be ruptured immediately and delivery assisted because the foal will rapidly become hypoxic and anoxic. 
  • Clients should be made aware of this condition because if they do not take action and await the arrival of a veterinarian, the foal will die of anoxia. 
  • Premature placental separation is associated with placentitis (the placenta is too thick to rupture at the cervical star area), twinning, inappropriate induction methods (PGF) and unknown causes. 
  • In many cases, the mare doesn't strain and the premature separation and failure to rupture interferes with delivery. 
  • The foal progressively becomes hypoxic, weak, and dead. 
  • This condition should be treated as an emergency with rupture of the membrane and delivery of the foal.

In any case, correction of dystocia should aim to minimize trauma to the mare.  

  • Elevation of the hindquarters with the mare under general anesthesia provides additional room to manipulate the fetus. 
  • Fetotomy is a viable solution, provided trained personnel and proper instruments are available. Otherwise, trauma to the mare is likely. 
  • Caesarian section is an excellent alternative if facilities and personnel are available. 
  • One of the biggest problems with fetotomy or caesarian section is the delay in making the decision to go forward with either option. 
  • If the decision is delayed, the mare becomes exhausted and the reproductive tract traumatized. 
  • The procedure and recovery then becomes more difficult. 
  • The benefit of timely decision making is shown by studies examining elective c-section in mares in which live foals were delivered, some mares had repeat sections in following years, others had vaginal delivery and so forth.


Induction of parturition

  • Induction of parturition in mares had a bad reputation for years because of inability to determine when the foal was mature enough for life outside the womb. 
  • Induction of parturition based on gestation length alone or even with the additional information of udder development and relaxation of the ligaments and cervix resulted in the delivery of premature foals that needed intensive care to survive and frequently died in spite of the care. 
  • With the knowledge of the changes in mammary secretion electrolytes, however, induction can now be performed safely. 
  • The criteria to be met before induction include 
    • 330 d gestation minimum, 
    • colostrum in the udder, 
    • relaxation of the ligaments and cervix and most importantly, 
    • changes in the mammary secretions of >400 ppm (10 mmol) calcium. This is the KEY CRITERIA.
    • Inversion of the Na:K ratio is also critical (K should be > Na in mammary secretions)

      Methods of induction  
  • It is advisable to place a jugular catheter before inducing parturition.

Oxytocin is the drug of choice.  

  • The dose used is related to the intensity of parturition and the time to delivery. 
  • The smoothest induction is with a low dose (5-10 IU bolus IV or 10 IU in 200 ml over 15 min). 
  • The hypothesis is that a small dose begins the cascade and the endogenous response carries it on. 
  • Other reported protocols include: single IM bolus (100 IU; 40-60 IU); multiple small IV injections (10-20 IU) every 10 min; IV boluses (20-40 IU) in 60 ml saline every 20 min; IV drip (60-80 IU) in 500 ml saline; but parturition is more rapid and forceful with these higher doses. 
  • The trend is toward smaller doses which seem more physiologic.

PGF2a is effective in inducing parturition but results in an increase in premature placental separation, dystocia and foal mortality. It is NOT recommended

Indications are that if criteria for induction are met (including Ca level of mammary secretions), fluprostenol is safe and effective but the time interval from treatment to parturition is longer and more variable than oxytocin.

Steroids given repeatedly in high doses will shorten gestation length but are ineffective for inducing parturition for practical purposes.

Postpartum disorders
Retained placenta
  • Retained placenta is rare due to the strong uterine contractions and microcotyledonary attachment of the placenta in mares. 
  • Retention usually occurs in the non-gravid horn. 
  • Unlike the cow, this should be treated as an emergency. 
  • Tissue breakdown and bacterial growth may lead to metritis - laminitis - septicemia complex. 
  • The placenta should be passed in 3 h, if not, initiate treatment prior to 4 -6 h postpartum. 
  • The aims of treatment are to stimulate release of the placenta, evacuate the uterus, encourage involution, control bacterial growth and prevent laminitis.

  • Treatment
    • Attempts to remove the placenta manually risk hemorrhage and trauma to the uterus. Manual removal is not recommended. 



  • Prior to 4 - 6 h after parturition
  • Re-distension of chorio-allantois may be attempted (Burn's technique)
  • This method is usually quite effective if there is only a single hole in the placenta at the cervical star area. 
  • Insert tube into placenta (not around it!) and distend with fluid (home made isotonic saline is good)
  • Distend placenta (stand back when the fluid rushes out)
  • Repeat until placenta releases

  • Oxytocin therapy.
  • The more effective oxytocin method is to administer the oxytocin in an IV drip (50 IU) in 500 ml saline over a 30 min period (this is the '5 method'...... 50 units, 500 mL, 0.5 hours)
  • Other methods include a large IM bolus of 80-100 IU or small IV doses (10-20 IU) repeated every 15 min. 
  • Always examine the placenta after passage to make sure it is all present
  • It is helpful to know the normal appearance to be able to identify pathology.  
  • After 4 - 6 h
    • Treatment should include broad spectrum systemic antibiotics, e.g. potassium penicillin (22,000 - 44,000 IU/kg, IV, QID) plus gentamicin (6.6 mg/kg, IV, SID) plus metronidazole (15 mg/kg, PO, BID). 
  • In addition, uterine lavage with saline will reduce the accumulation of debris in the uterus. 
  • The retention should be manually re-evaluated, at least daily. 
  • Exercise is helpful, provided there are no signs of laminitis. 
  • Make sure that tetanus vaccination is current. If not, administer tetanus toxoid. 
  • Monitor the mare for signs of metritis - laminitis - septicemia complex.

Metritis - laminitis - septicemia complex.  

  • This problem may develop due to gross contamination at foaling or retained placenta. 
  • Affected mares exhibit depression, anorexia, congested mucous membranes, elevated temperature, pulse, and respiration rate. 
  • Signs appear as early as 12 h postpartum. 
  • Treatment consists of evacuating the uterus by large volume lavage (with saline) to eliminate debris and toxins. 
  • Systemic therapy consists of systemic antibiotics, fluids, anti-inflammatories, tetanus toxoid, monitoring for laminitis, etc. as outlined previously for retained placenta.

Delayed uterine involution  

  • Normally, involution in the mare is very fast. 
  • By 7 d postpartum the uterus is 2 - 3 times the size of the uterus of a barren mare. 
  • Mares with delayed uterine involution may have a discharge, occasionally exhibit dullness or mild pain and on rectal exam have a large, baggy, flaccid uterus. 
  • Ultrasound exam reveals excessive fluid in the uterus. 
  • Treatment consists of uterine lavage, oxytocin (50-100 U in 500 ml IV drip, or multiple small doses), exercise (provided there are no signs of laminitis), antibiotics, etc. Oxytocin therapy is especially important in cases where the foal is dead because then the normal endogenous release of oxytocin in response to suckling is absent.

Postpartum hemorrhage 

  • Hemorrhage can occur into the broad ligament dissecting between the myometrium and serosa. 
  • Clinical signs are characterized by a slow onset (12-48 h), with signs of colic, sweating, pale mucous membranes and elevated pulse. 
  • There may be no signs but a hematoma is found on the prebreeding exam. 
  • Diagnosis is by rectal exam and ultrasonography, aided by abdominocentesis. 
  • Treatment is basically supportive care and consists of keeping the mare quiet and providing analgesics.

Uterine prolapse 

  • This is a true emergency in the mare. 
  • Even with rapid attention, the prognosis for survival is estimated as 50%. 
  • The uterus should be cleaned and replaced as soon as possible. 
  • The vulva is not sutured as in the cow. 
  • Treat the mare for shock if needed. 
  • Administer anti-inflammatories, systemic antibiotics, tetanus toxoid, oxytocin.

Uterine tears 

  • The most common location is dorsal, just anterior to the cervix. 
  • Initial treatment is for hemorrhagic shock. 
  • Surgical repair is indicated, unless the tear is small and dorsally located. 
  • They often lead to peritonitis. 
  • Medical treatment consists of oxytocin (e.g. 20 IU every 2 h) and / or ergonovine 1-3 mg i.m., repeated every 2-4 h., along with antibiotics, and NSAID's. 
  • Massage per rectum after surgical repair is indicated to prevent adhesion formation.

Recto-vestibular and perineal lacerations  

  • These are more common in maiden mares due to a tight vaginal-vestibular sphincter. 
  • They also occur in cases of fetal malpositioning, relative fetal oversize and overzealous assistance. 
  • These will be covered more thoroughly in the surgery sessions. 
  • Basically, immediate repair can be attempted but if not done immediately after occurrence, repair should be delayed until the initial inflammation has subsided.

Cervical laceration  

  • Trauma to the cervix may interfere with its normal valve like action, affecting its competency to permit breeding and maintain pregnancy. 
  • Damage is often iatrogenic following dystocia or fetotomy. 
  • Treatment is surgical repair bur because the surgery is difficult and often unsuccessful, a BSE is recommended before surgery.
  • Cervicitis / Vaginitis
  • Necrotic vaginitis and/or cervicitis possible after dystocia

  • Can be life threatening

  • Can interfere with urination, defecation (swelling, abscess formation)
  • Treat with antibiotics, NSAIDs, Tetanus toxoid  

Gastrointestinal complications  

  • Various complications can occur, including constipation, small colon bruising, and rupture of the rectum, cecum, or small colon. 
  • Signs of colic and peritonitis follow. 
  • The diagnosis can often be confirmed with paracentesis.


Elective termination of pregnancy

  • Numerous indications exist, with twinning and inadvertent breeding being some of the most common. 
  • The choice of method depends greatly on the stage of gestation. 
  • Before 5-7 d post ovulation there is no effective method. The embryo has not entered the uterus yet and the CL is not responsive to PGF. 
  • From 5 d post ovulation until the endometrial cups form at about 35 d, any number of methods will terminate pregnancy. 
    • Probably the simplest is an injection of PGF. 
    • Uterine lavage or manual crushing will also end the pregnancy. 
    • In the case of twins, where it is desired to maintain one vesicle while destroying the other, isolation of one vesicle and manual crushing is the preferred method.
      •  Because of the mobility of the early vesicles, isolation and crushing is best performed before d 16. 
  • After the endometrial cups have formed, PGF can still be used to terminate pregnancy but multiple injections may be necessary.
    •  Uterine lavage or uterine infusion can also be used, as well as manual crushing if it is early enough to be able to grasp the vesicle. 
  • Various methods have been employed to terminate one of a set of twins while allowing the other to continue to term. 
    • Currently one of the most promising is ultrasound guided aspiration. 
      • Although only about a third of mares treated with this technique will carry the remaining foal to term, this is a much higher percentage than would be successful if no intervention was practiced.
    • Fetal decapitation at about 75 days is the best method to terminate twins.
    • Twin Reduction by Cervical Dislocation (as told by Karen Wolfsdorf)

      • Best time to perform surgery is between 75 to 85 days

      •  Ultrasound to locate and identify fetuses, choose the one with the least surface area or closest to the tip of the horn

      • Give Banamine pre-op

      • Give 0.5 cc detomidine

      • Clip and give local block

      • Give another 0.5 cc detomidine

      • Give 1.0 cc propantheline (This is critical if skip this, uterus will be too turgid to be able to perform task - available from HGD Pharmacy)

      • Grid incision (big enough to permit arm in abdomen)

      • Locate fetus, dislocate cervix by rolling between thumb and second finger (bigger fetuses sort of like popping a cork on a bottle)

      • Routine closure

      • Post-Op Banamine q 12 h for 2 d

      • Double dose Regumate for 30 d

      • Pen/Gent for 3 d, then 7 more d of SMZ


contributed by Bruce E Eilts and modified on 30 July 2007

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contributed by Bruce E Eilts on 25 September 2012


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