Care of the Pregnant Mare: 7 Proven Steps

Introduction: Biological and Economic Foundations

The meticulous care of the pregnant mare and foal represents one of the most complex and sensitive branches of veterinary medicine and the global horse industry. The journey from successful insemination to the weaning of a physically sound and psychologically stable foal is not merely a series of automatic biological events; it is a path fraught with physiological and environmental challenges requiring precise and informed managerial intervention.

Modern scientific literature indicates that “Fetal Programming” plays a pivotal role in determining a horse’s future athletic and health potential. Factors such as nutrition, the uterine environment, and peripartum care directly influence bone quality, immune system efficiency, and even the foal’s behavioral stability for years post-weaning.

In the context of specialized animal production, the pregnant mare (Broodmare) is a high-value “biological production unit.” The last trimester of pregnancy and the Peripartum Period represent the most critical time window. During this period, fetal growth accelerates exponentially, and radical hormonal and immunological changes occur in preparation for labor and lactation. Any mismanagement in nutrition or preventive care during this phase can lead to dire consequences, ranging from late-term abortion and the birth of Compromised Neonates to life-threatening complications for the mare, such as retained placenta and laminitis.

This research report offers a comprehensive investigative analysis of standard and advanced practices regarding the care of the pregnant mare. It is based on the latest recommendations from the American Association of Equine Practitioners (AAEP) and the National Research Council (NRC). The report aims to provide specialists and breeders with an accurate reference covering all technical aspects, from precise nutritional adjustments in late pregnancy and strict vaccination protocols to labor prediction mechanisms, obstetric emergency management, and safe weaning strategies.

1. Physiological and Nutritional Management in the Last Trimester

The final three months of gestation (Month 9 to Month 11) constitute a critical transitional phase in the mare’s physiology. Research data indicates that the fetus gains approximately 75% of its final weight during this brief period, imposing immense metabolic demands on the mother. This accelerated growth requires not only an increase in calories but a complete restructuring of the diet to meet specific tissue and bone building needs.

Nutritional Dynamics: The Shift from Maintenance to Fetal Building

In the early stages of pregnancy (Months 1–8), the mare’s nutritional requirements are relatively close to those of maintenance horses, as fetal growth is slow. However, by the fifth month, the NRC recommends starting gradual adjustments, the pace of which accelerates sharply in the last trimester.

Protein and Energy Requirements

Protein is the fundamental building block for fetal tissues and the placenta. Nutritional tables show a marked increase in the daily requirement for Crude Protein. While a mare in maintenance or early pregnancy needs about 630 grams of protein daily, this figure rises to 759 grams in the eighth month and continues to climb, reaching 893 grams daily by the eleventh month.

This quantitative increase must be matched by a focus on quality, specifically essential amino acids like Lysine and Methionine, which are necessary for fetal protein synthesis. Protein deficiency during this stage affects not only the foal’s birth weight but may also compromise the quality of Colostrum and subsequent milk production, threatening the foal’s passive immunity.

Parallel to protein, Digestible Energy (DE) requirements rise. Data indicates an increase in need from 16.7 Mcal/day in early pregnancy to approximately 21.4 Mcal/day in the eleventh month. However, extreme caution must be exercised to avoid oversupplying energy to prevent obesity, which is linked to Dystocia (difficult birth) and metabolic disorders.

Trace Minerals and Their Role in Skeletal Development

Mineral nutrition becomes paramount in the care of the pregnant mare, particularly in the last trimester. The fetus stores reserves of Trace Minerals in its liver for use during the first months of life, given that natural mare’s milk is poor in these elements.

Copper & Zinc: These elements play a crucial role in cartilage and bone formation. Copper deficiency, in particular, has been linked to increased rates of Developmental Orthopedic Diseases (DOD) in foals. Therefore, it is advisable to use balanced supplements (Balancer Pellets) to ensure correct ratios of these minerals.
Calcium and Phosphorus: The need for these increases significantly to ensure calcification of the fetal skeleton without depleting the mother’s bone reserves.
Iodine: This represents a double-edged sword; the equine fetus is extremely sensitive to iodine levels. Deficiency or excess (which may come from supplements like Kelp) can lead to Goiter in the foal, potentially causing respiratory issues and general weakness at birth.

Body Condition Score (BCS) Management

Assessing body condition is a vital management tool. The goal is to maintain the mare at a score between 5 and 6 (on a scale of 1 to 9).

Thin Mare (BCS < 5): Lacks the fat reserves necessary to support lactation, which may lead to muscle wasting, poor milk production, and delayed Rebreeding post-foaling.
Obese Mare (BCS > 7-8): Faces higher risks of insulin resistance and may suffer from fat accumulation in the birth canal, complicating the foal’s exit, as well as heat and cardiac stress during labor.

2. The Immunological Protocol: Advanced Vaccination Strategies

Vaccinating the pregnant mare aims not only to protect her but is the only means of providing immune protection to the newborn foal during its first months. The foal is born with an immature immune system and is “Agammaglobulinemic” (without antibodies) because the equine placenta does not allow the passage of antibodies. Consequently, the foal relies entirely on Colostrum to acquire passive immunity.

Prevention of Viral Abortion (EHV-1)

Equine Herpesvirus Type 1 (EHV-1) is the leading cause of Rhinopneumonitis Abortions, which often occur in the last trimester, suddenly and without warning signs. To control this risk, the AAEP recommends a strict protocol:

Schedule: The mare must be vaccinated at the beginning of the 5th, 7th, and 9th months of pregnancy.
Vaccine Type: Inactivated/Killed Vaccines licensed specifically for abortion protection (such as Pneumabort-K® or Prestige® Prodigy®) must be used. Vaccines designed solely for respiratory disease may not provide sufficient protection for the fetus against abortion storms.
Biosecurity: In addition to vaccination, pregnant mares must be isolated from transient horses (like show and racehorses) and new arrivals to reduce the risk of exposure to active viral strains.

Enhancing Passive Immunity (Pre-foaling Boosters)

To ensure colostrum contains the maximum possible concentration of antibodies, the mare should be given booster doses of core vaccines 4 to 6 weeks before the expected due date. This protocol includes:

Tetanus: Vital for protecting the mare from reproductive tract contamination during birth and protecting the foal from neonatal tetanus via the umbilicus.
Rotavirus: Given in a series of three doses (Months 8, 9, 10) in farms experiencing viral diarrhea issues in neonates. This vaccine significantly reduces disease severity and mortality rates in foals.
Endemic Diseases: Such as Equine Influenza, Encephalomyelitis (EEE/WEE), and West Nile Virus (WNV).
Rabies: Recommended annually; can be scheduled pre-foaling to increase maternal antibody transfer to the foal.

3. Logistical and Biological Preparation for Foaling

As the end of the gestation period approaches (naturally ranging between 320 and 360 days, averaging 335-340 days), accurate prediction of the foaling date and environmental preparation become decisive factors in reducing neonatal mortality rates. Most births occur at night between 9 PM and 8 AM, increasing the importance of monitoring.

Labor Prediction Indicators

The mare exhibits a series of physiological changes predicting the approach of labor, but their accuracy varies significantly between individuals.

Physical Signs

Udder Development: Filling and distension begin 2–6 weeks before foaling, but may be delayed in Maiden Mares.
Ligament Relaxation: Distinct softening occurs in the Croup muscles and around the tail head, giving the hindquarters a “dropped” appearance, accompanied by elongation and relaxation of the vulva 7–19 days prior.
Waxing: The appearance of sticky yellow droplets (dried colostrum) on the teat tips. This is a strong sign; approximately 70–95% of mares foal within 24–48 hours of waxing. However, some mares may foal without waxing, or wax two weeks early.

Milk Chemistry Testing

Due to the unreliability of visual signs alone, modern veterinary medicine utilizes mammary secretion analysis for accurate prediction. This relies on ionic changes in the milk pre-foaling.

Calcium Carbonate Test: Calcium concentration in milk rises sharply before birth. Using test kits like FoalWatch™ or water hardness strips, when the concentration exceeds 200 ppm, the probability of foaling within 24 hours reaches 98%.
pH Test: Mare’s milk tends to drop in pH (becoming more acidic) as birth approaches.

Preparing the Foaling Environment and Emergency Kit

The mare should be moved to the foaling location (Stall) weeks before the due date to develop antibodies against the specific bacteria of the new environment. The area must be spacious (at least 4×4 meters), bedded with clean straw (straw is preferred over shavings to avoid dust inhalation or adherence to the wet foal), and well-lit and ventilated.

Foaling Kit Inventory

The kit must be ready, sterile, and contain the following tools to ensure a rapid response to any emergency:

Table 3: Checklist for Essential Foaling Kit Contents

Category	Item	Purpose and Use
Hygiene & Sterilization	Mild Liquid Soap (e.g., Ivory)	Washing the mare’s perineum and udder before birth.
	Chlorhexidine Solution (Nolvasan) Diluted	Disinfecting the foal’s umbilical cord (1:4 ratio).
	Clean, Large Towels	Drying the foal and stimulating its breathing.
	Long, Sterile Exam Gloves	For obstetric intervention or checking fetal position.
	Thick Plastic Trash Bag	To store the placenta after expulsion for veterinary examination.
Medical Tools	Blunt Scissors (Mayo Scissors)	To open the “Red Bag” in emergencies or cut the umbilical cord.
	Umbilical Clamp	To stop umbilical bleeding if cut abnormally.
	Enema	Sodium phosphate or soapy water to treat meconium impaction.
	Digital Thermometer	Monitoring the temperature of the mare and foal.
Logistical Support	Flashlight with Extra Batteries	Because most births are nocturnal, and power may fail.
	Stopwatch	To record labor stage times accurately (1-2-3 Rule).
	Veterinarian’s Number	Clearly written for emergencies.
	Phone Charger	To ensure continuous communication.

4. Dynamics of Labor and Parturition

Equine birth is characterized as being “explosive” and extremely rapid compared to ruminants or humans. This speed means the margin for error is very narrow, and any delay necessitates immediate intervention. The process is divided into three distinct physiological stages.

Stage 1: Preparation & Positioning

This stage begins with invisible uterine contractions aimed at rotating the fetus and dilating the cervix.

Behavior: The mare shows signs of restlessness, sweating (especially behind the elbows and flank), tail raising, frequent urination, and looking at the flank (signs resembling mild colic).
Physiology: The fetus is in “Dorsal Recumbency” (on its back) for most of the pregnancy. During this stage, the fetus rotates to assume “Ventral Recumbency” (on its stomach) with the head and forelegs extended toward the birth canal.
Duration: Usually lasts 1 to 4 hours.
End: This stage ends with the rupture of the outer Chorioallantois membrane and the release of thick fluid (“breaking water”), signaling the start of Stage 2.

Stage 2: Expulsion of the Fetus

This is the critical phase where the foal enters the world.

Duration: Very fast, typically ranging between 15 and 30 minutes.
Normal Appearance: A translucent bluish-white sac (Amnion) should appear, containing two front hooves (soles facing down), followed by the nose resting on the legs, then the head and shoulders.
Intervention: Once the shoulders are out, the rest of the body exits easily. The mare often remains lying down for several minutes after the foal exits; this is healthy behavior allowing up to 30% of placental blood to pump into the foal via the umbilical cord before it ruptures.

Stage 3: Placenta Expulsion

Following the birth of the foal is the expulsion of fetal membranes.

Duration: Usually occurs within one hour and must be completed within 3 hours maximum.
Procedure: Once the placenta is expelled, it should be placed in the designated bag and kept in a cool place for the veterinarian to examine for completeness (presence of a complete “F shape” forming the uterine horns) and absence of tears indicating retained fragments inside the uterus.

5. Obstetric Emergencies

Due to the speed of equine birth, any deviation from the normal path requires an immediate and decisive response. Prior knowledge of these conditions is a critical aspect of the care of the pregnant mare.

“Red Bag” Delivery

Medically known as Premature Placental Separation, this is an extreme emergency.

Pathophysiology: Normally, the outer amniotic sac (placenta) ruptures at the cervix to allow the white amniotic sac to pass. In a “Red Bag” case, the entire placenta detaches from the uterine wall and exits as a single mass with the fetus. Since the placenta is the fetus’s oxygen source, its separation means immediate oxygen deprivation while the foal is still in the canal.
Potential Causes: Placentitis, stress, or Fescue Toxicity (causing thickened placenta).
Signs: Appearance of a thick, velvety red sac at the vulva instead of the translucent white sac.
Immediate Action: There is no time to wait for a vet. The breeder must rupture the red bag immediately (with scissors or fingers) and manually deliver the foal as fast as possible to enable breathing; otherwise, it will suffer from Hypoxia or death.

Retained Placenta

The placenta is considered retained if it does not pass within 3 hours of birth.

Risks: Horses are highly sensitive to necrotic tissue remaining in the uterus. Rapid decomposition of the placenta leads to massive bacterial growth, causing Endotoxemia. Bacterial toxins trigger a cascade of inflammatory reactions often leading to Laminitis/Founder, a painfully debilitating and potentially fatal disease for the mare.
Treatment: It is strictly forbidden to pull the placenta by force, as this may cause hemorrhage or tearing, leaving small fragments that cause chronic infection. Medical treatment involves Oxytocin injections at calculated doses to stimulate contractions, Uterine Lavage to remove debris and toxins, and coverage with antibiotics and anti-inflammatories. Some advanced protocols include the “Burns Technique” (filling the placenta with water to aid separation).

Dystocia

Any abnormal position (e.g., appearance of one leg, hoof sole facing up, or no head appearance) requires immediate veterinary intervention.

The Golden Rule: If the fetus does not advance within 10–20 minutes of strong pushing, there is a problem.

6. Neonatal Medicine and the Golden Protocol (1-2-3 Rule)

After the foal is safely delivered, the vital assessment phase begins. Veterinarians and professional breeders rely on the “1-2-3 Rule” as a global standard for evaluating newborn health and determining the need for intervention.

The 1-2-3 Timeline

First Hour (Standing): The foal must stand on its feet independently within one hour of birth. Standing is essential for full lung expansion, circulating blood flow, and reaching the udder. A foal that fails to stand within two hours may suffer from neurological issues (Dummy Foal Syndrome).
Second Hour (Nursing): The foal must begin Nursing effectively (Sucking Reflex) and swallowing within two hours. The foal is born with very low energy reserves (glycogen) in the liver. Delayed nursing exposes it to the risk of Hypoglycemia rapidly. If the foal does not nurse, the mare must be milked and the foal bottle-fed.
Third Hour (Placenta Passage): As previously mentioned, the mare must expel the placenta by the third hour to avoid complications.

Umbilical Care

The umbilical cord is an open gateway for bacteria to enter directly into the foal’s bloodstream, potentially causing “Navel Ill” (Omphalophlebitis) or Septic Arthritis.

Antiseptic: The debate over using Iodine has been settled in many modern recommendations in favor of Chlorhexidine.
Diluted Chlorhexidine (1:4): Considered the best option as it is effective against bacteria, less irritating to tissues, and has a longer residual effect.
Diluted Iodine Solution: Can be used, but Strong Iodine (7%) must be avoided as it causes chemical burns and necrosis (Scalding) of surrounding tissues.
Protocol: Dip the navel (do not just wipe) 2–3 times daily for two days or until completely dry.

Assessment of Passive Immunity Transfer (IgG Testing)

Due to the placental type (Epitheliochorial), antibodies do not pass from mare to foal during pregnancy. The foal relies entirely on absorbing Immunoglobulins (IgG) from colostrum through the small intestine during the first 12–24 hours. After 24 hours, the intestinal cells “close” and stop absorption.

Testing: A blood test (such as SNAP ELISA or Zinc Sulfate Turbidity) must be performed on the foal 12–24 hours after birth to assess IgG levels.
Interpreting Results:
- > 800 mg/dl: Adequate Transfer.
- 400 – 800 mg/dl: Partial Failure – requires monitoring and potentially preventative treatment.
- < 400 mg/dl: Failure of Passive Transfer (FPT).
- < 200 mg/dl: Complete and critical failure.
Treatment: In cases of failure (especially if the window for intestinal absorption has passed, i.e., after 24 hours), the only treatment is Intravenous Plasma Transfusion rich in antibodies to protect the foal from Sepsis.

Meconium Impaction

Meconium is the foal’s first feces (dark, sticky substance). It should pass during the first few hours. Impaction is the most common cause of colic in neonates, especially males (due to their narrower pelvis).

Symptoms: Continuous Straining to defecate, raising and arching the tail, rolling, and colic.
Treatment: Enemas are used as the first line of treatment. Commercial phosphate enemas (Fleet Enema) are effective. Warm soapy water enemas or Acetylcysteine (Retention Enema) are used for stubborn cases to break down the mucous bonds.

7. Nutrition and Growth During Lactation

Lactating Mare Nutrition: Peak Metabolic Demand

The mare’s nutritional requirements reach their peak during lactation (especially Months 1–3), as she needs to produce massive amounts of milk (up to 3% of her body weight daily).

Energy and Protein: Energy needs increase by up to 84%, and protein needs by 232% compared to maintenance status. Concentrated feed amounts must be increased gradually, and high-quality forage (like Alfalfa) provided ad libitum.
Weight Management: Failure to meet these needs will cause the mare to lose weight rapidly, reducing milk quality and delaying the next conception. Adding fats and oils to the diet is an effective way to increase calories without increasing dangerous starches.

Supplemental Feeding for the Foal (Creep Feeding)

Although mother’s milk is the primary food, by the third month, the foal’s nutritional needs exceed what milk alone provides, especially regarding minerals and protein.

Concept: Providing specialized concentrated feed for foals in an isolated area (Creep Feeder) that allows the foal access while preventing the mare.
Benefits:
- Bridging the Nutritional Gap: Providing necessary Copper, Zinc, and Calcium to prevent Developmental Orthopedic Diseases (DOD).
- Facilitating Weaning: Accustoming the foal’s digestive system to digesting grains and fiber reduces nutritional and psychological shock at weaning and prevents the Growth Slump after separation from the mother.
Specifications: The feed should contain 14–16% high-quality protein, with a precise balance between Calcium and Phosphorus (Ratio of 0.8% Ca and 0.5% P).

8. Weaning Strategies and Stress Management

Weaning is one of the most stressful events in a young horse’s life, combining emotional separation from the mother with a complete nutritional shift. It is typically performed between 4 and 6 months of age.

Weaning Methods: Gradual vs. Abrupt

Behavioral and hormonal studies (measuring Cortisol) confirm that the weaning method directly affects foal welfare.

Abrupt Separation: Involves immediate and total separation (visually and audibly). This method causes the highest stress levels, increases the risk of injury due to escape attempts, and leads to bad stereotypical behaviors (Stereotypies) and compromised immunity.
Gradual/Interval Weaning: Considered best for welfare. It involves allowing the foal to see and touch its mother through a safe fence for a few days before total separation, or removing mothers one by one from a herd of foals (Pasture Weaning). Research has shown that gradually weaned foals exhibit lower cortisol levels, eat better, and show fewer anxiety behaviors (less whinnying and running) compared to abrupt weaning.

Management to Reduce Stress

Pre-feeding: As mentioned, Creep Feeding weeks before weaning reduces nutritional stress.
Companionship: Weaning foals in pairs or groups reduces loneliness. The presence of a calm, adult “Nanny Horse” with the weaned foals helps soothe them and teaches proper social behavior.

Conclusion

Effective care of the pregnant mare and foal is not merely a routine task but a long-term investment in the health and competitive capability of the next generation of horses. Through a deep understanding of the physiology of the last trimester, application of precise vaccination protocols (especially against EHV-1), and vigilant preparation for critical birthing moments, breeders can significantly reduce risks. Adhering to modern care standards—such as IgG testing, umbilical care with Chlorhexidine, thoughtful supplemental nutrition, and Gradual Weaning—makes the fundamental difference between producing ordinary horses and horses possessing the highest degrees of health, immunity, and performance.

Table 4: Summary of Preventive and Managerial Actions by Timeline

Timeline Stage	Key Action	Notes and Warnings
Month 5, 7, 9 of Pregnancy	EHV-1 Vaccine (Abortion)	Use Pneumabort-K or Prodigy vaccines exclusively.
Month 10 (4-6 weeks pre-foaling)	Booster Vaccines (Tetanus, Flu, Rotavirus)	To raise antibody levels in Colostrum.
2-4 weeks pre-foaling	Open Monitoring File (Calcium Test)	>200 ppm indicates foaling within 24 hours.
During Labor	Monitor “Red Bag”	Rupture bag immediately if it appears velvety red.
Hour 1-3 Post-Foaling	1-2-3 Rule	Stand (1), Nurse (2), Placenta (3).
12-24 Hours Post-Foaling	IgG Test	Target >800 mg/dl; Intervene with Plasma if failed.
Month 1-2 of Age	Start Creep Feeding	To support growth and reduce weaning stress later.