Horse Pregnancy Signs: A Complete Guide for Mare Owners
Recognizing mare pregnancy signs is essential for every horse owner who wants to ensure the health of both mare and foal. From subtle behavioral shifts to physical changes, each stage of pregnancy reveals clues that help you track progress and prepare for foaling.
In this guide, we will break down the key signs, diagnostic methods, mare gestation periods by breeds, and best practices for managing a healthy pregnancy, giving you clear insights to support your mare every step of the way.
Behavioral Changes
One of the first areas where you may notice mare pregnancy signs is in her behavior. Mares often exhibit shifts in temperament as pregnancy begins. These changes can mimic or mask heat cycles, making observation necessary.
Changed Appetite: Pregnant mares may eat more or less than usual. Gradual increases are normal as the fetus grows, while sudden changes could signal health issues.
Altered Social Behavior: A mare may withdraw from herd interactions or avoid stallions, reflecting hormonal changes in early pregnancy.
Mood Swings: Hormonal fluctuations can cause irritability or unexpected reactions to handling. Monitoring patterns helps differentiate normal pregnancy behavior from stress responses.
Protective Attitude: Some mares become more defensive around foals, other horses, or humans, particularly later in gestation.
Calmer Demeanor: Conversely, some mares show increased calmness and reduced restlessness, which is a positive mare pregnancy sign.
Physical Signs
Physical changes provide stronger clues of pregnancy, though most are not visible until several weeks into gestation. Careful observation and record-keeping are critical for catching these early.
Change in Body Condition: As weeks progress, mares often gain subtle weight through the abdomen, though this can be confused with fat from feed.
Udder Development: Swelling of the udder usually occurs late in the mare pregnancy stage, often in the final trimester, as the body prepares for lactation.
Vulva Softening: Hormonal changes can cause the vulva to relax and appear looser than usual.
Decreased Cycling: A mare that does not return to heat within 18–23 days after breeding is a strong indicator of conception.
Additional Signs
Beyond behavior and physical changes, mares may show other subtle pregnancy signs that help you determine whether to schedule a veterinary check.
Increased Appetite: Many pregnant mares gradually eat more, reflecting the growing nutritional needs of the fetus.
Visible Fetal Movement: In the later stages of mare pregnancy, small kicks or shifts may be seen in the abdomen.
Milk Secretion: Closer to foaling, you may notice milk or waxy buildup on the teats. However, early milk leakage can signal issues and should be discussed with a veterinarian.
Shinier Coat: Some owners report a healthier-looking coat, possibly due to hormonal balance during pregnancy.
While none of these signs alone confirms pregnancy, together they suggest a mare pregnancy and can confirm the pregnancy through diagnosis.
Horse Pregnancy Diagnosis Methods
Because mare pregnancy signs can be subtle or mistaken for regular cycle changes, veterinary confirmation is essential. Modern diagnostics give you several options depending on how far along your mare is in gestation.
1. Rectal Palpation
Rectal palpation is a hands-on method where a veterinarian gently feels the mare’s uterus through the rectal wall to detect early pregnancy changes. This technique helps identify the presence of a conceptus and assess uterine tone and development.
When: Typically 16–20 days post-breeding.
Advantages: Quick, inexpensive, and provides immediate confirmation.
Limitation: Requires an experienced veterinarian; risk of injury if done improperly.
2. Mare Pregnancy Ultrasound
A mare pregnancy ultrasound uses sound waves to visualize the embryo or fetus within the uterus. Ultrasound allows early detection of pregnancy, monitors fetal heartbeat, and can detect twins or abnormalities, making it highly reliable.
When: As early as 14 days after breeding; follow-up scans are recommended at 25–30 and 60 days.
Limitation: Requires equipment and trained personnel; higher cost than palpation.
3. Blood Tests
Blood tests measure pregnancy-specific hormones, such as equine chorionic gonadotropin (eCG) or progesterone, to confirm gestation. These tests provide hormonal evidence of pregnancy and are particularly useful for mares that are difficult to handle.
When: Around 40–100 days post-breeding.
Advantages: Non-invasive and effective method for mares that are difficult to handle.
Limitation: Cannot detect twins; may give false positives in certain conditions.
4. Urine Tests
Urine tests detect pregnancy-related hormones secreted in the mare’s urine. While less commonly used today, they offer an alternative when blood sampling or ultrasound is not feasible.
When: After the first 40 days of gestation.
Advantages: Non-invasive, simple to collect.
Limitation: Less reliable than ultrasound or blood tests; cannot provide fetal details.
Mare Gestation Periods by Breeds
On average, the mare pregnancy length is about 340 days, though it can range from 320 to 360 days. The duration often varies slightly between breeds, as well as with season, nutrition, and individual mares.
Racing Breeds Gestation Period
Code
Breed
Average Gestation Period
TB
Thoroughbred
~340 days
QH
Quarter Horse
~340 days
SB
Standardbred
~341 days
AR
Arabian
~339 days
Sports Breeds Gestation Period
Code
Breed
Average Gestation Period
KWPN
Dutch Warmblood
~341 days
HAN
Hanoverian
~340 days
TRAK
Trakehner
~340 days
Utility Breeds Gestation Period
Code
Breed
Average Gestation Period
PT
American Paint
340 days
AP
Appaloosa
~342 days
MS
Mustang
~340 days
CLY
Clydesdale
~340 days
PER
Percheron
~342 days
SH
Shire
~340 days
Mare Pregnancy Stage
Understanding the mare's pregnancy stage helps you provide targeted care for both mare and foal. Each trimester has distinct developmental milestones, visible signs, and nutritional requirements to ensure a healthy pregnancy.
First Trimester (Days 0–114)
The first trimester focuses on early embryo development and implantation in the uterus. Mares often show subtle behavioral and physical changes, making careful observation essential.
Development: Embryo implants and major organs begin forming; heartbeat detectable around day 25 via ultrasound.
Nutritional Needs: Maintenance-level feed with high-quality forage; balanced vitamins and minerals to support early fetal growth.
Care Tip: Minimize stress, avoid strenuous activity, and ensure routine veterinary check-ups.
Second Trimester (Days 115–226)
During this stage, the fetus grows steadily, and the pregnancy stabilizes. Mares may regain normal energy and appearance, though subtle abdominal changes continue.
Development: Organs and skeletal structures mature; the placenta fully develops.
Visible Signs: Slight abdominal enlargement, calmer demeanor, continued absence of heat cycles.
Nutritional Needs: Gradual increase in energy and protein; maintain consistent forage intake.
Care Tip: Regular deworming, dental care, and monitoring of weight and body condition.
Third Trimester (Days 227–340)
The third trimester involves rapid fetal growth, preparing both mare and foal for birth. Physical signs become most pronounced, and nutritional demands rise significantly.
Development: Rapid fetal growth; organ and musculoskeletal systems fully develop.
Visible Signs: Noticeable belly, udder development, fetal movement, waxing of teats near foaling.
Nutritional Needs: Increase feed by 20–25%, emphasizing high-quality protein, calcium, and vitamins; ensure constant water access.
Care Tip: Monitor closely for foaling signs, reduce stress, and prepare the foaling stall and supplies.
Stage
Days
Key Events
First Trimester
0–114
Embryo implantation, organ formation, early heartbeat, and subtle behavioral changes
Second Trimester
15-226
Organ maturation, skeletal development, placental growth, and subtle abdominal changes
Third Trimester
227-340
Rapid fetal growth, udder development, fetal movement, and preparation for foaling
Best Practices for a Healthy Mare Pregnancy
Once you’ve identified the mare's pregnancy signs and confirmed through diagnostics, your focus shifts to management. Proper care ensures both the mare and foal remain healthy throughout the mare's pregnancy period.
Nutritional Management
Feeding requirements change as the mare’s pregnancy stage progresses.
First Two Trimesters: Your mare’s energy demands remain similar to maintenance. High-quality forage with balanced vitamins and minerals is enough.
Final Trimester: Nutritional needs rise by about 20–25%. Supplement grain or concentrates with high protein, calcium, and phosphorus.
Important Nutrients: Vitamin E, selenium, and copper support fetal development.
Water: Provide free access to clean water at all times.
Health
Routine veterinary care is essential during pregnancy.
Vaccinations: Follow an updated vaccination schedule, including boosters for equine herpesvirus (EHV-1) to reduce abortion risk.
Deworming: Use a veterinarian-approved parasite control program, especially in the last trimester.
Dental Care: Float teeth if needed before late pregnancy to improve feed efficiency.
Environment and Stress Management
Your mare’s living environment directly impacts her pregnancy success.
Clean and Dry Shelter: Ensure stalls are well-ventilated, free of dampness, and regularly cleaned to prevent infections.
Safe Pasture and Turnout: Provide secure fencing and remove hazards; allow regular turnout for light exercise to support circulation and muscle tone.
Temperature and Weather Control: Protect mares from extreme heat, cold, or wet conditions, which can increase stress and impact health.
Herd Management: Avoid overcrowding and minimize exposure to aggressive herd members to prevent injury and stress.
Consistent Routine: Maintain predictable feeding, handling, and exercise schedules to reduce anxiety and hormonal disruption.
Monitoring and Preparation
Observation and record-keeping are key tools.
Behavioral Tracking: Record appetite, mood, and activity changes weekly to detect early pregnancy issues.
Physical Checks: Monitor abdominal growth, udder development, and fetal movement; document any unusual swelling or discharge.
Veterinary Follow-ups: Schedule regular check-ups, including mare pregnancy ultrasound and vaccinations, to ensure healthy progression.
Foaling Stall Preparation: Set up a clean, comfortable stall with fresh bedding 4–6 weeks before the expected foaling date.
Foaling Supplies and Emergency Plan: Keep necessary equipment, veterinary contacts, and a foaling kit ready to address any complications promptly.
Common Pregnancy Issues in Mare
Even with proper care, complications can arise. Understanding potential problems helps you act quickly if issues occur.
Trouble Getting a Mare in Foal
Some mares struggle to conceive despite multiple breeding attempts. This can be due to reproductive health issues or management factors.
Signs: Repeated failure to conceive after multiple cycles.
Causes: Uterine infections, poor semen quality, improper timing of breeding.
Prevention: Use breeding software to track heat cycles and cover dates accurately; conduct pre-breeding exams.
Treatment: Veterinary intervention with uterine treatments, hormone therapy, or improved breeding management.
Early Pregnancy Loss (Resorption)
Mares may lose the pregnancy in the first 40–60 days, often without clear external signs. Early loss can be detected through a mare pregnancy ultrasound.
Signs: Return to heat, lack of fetal heartbeat on ultrasound, and sometimes mild vaginal discharge.
Causes: Inadequate feed, poor-quality forage, or overfeeding without exercise.
Prevention: Provide a balanced diet with quality forage, supplements, and controlled grain intake.
Treatment: Adjust nutrition with veterinary guidance and monitor weight through regular body condition scoring.
Fescue Toxicity (from Endophyte-Infected Grass)
Tall fescue grass infected with endophyte fungus can cause severe late-pregnancy complications in mares.
Signs: Prolonged pregnancy, absence of milk production, weak or stillborn foals.
Causes: Ingestion of toxic endophyte-infected fescue.
Prevention: Remove mares from fescue pastures 60–90 days before foaling; test forage when unsure.
Treatment: Administration of domperidone under veterinary supervision to restore milk production and reduce risks.
Laminitis or Lameness While in Foal
Pregnant mares may suffer from laminitis (hoof inflammation) or lameness, which can worsen due to added weight and hormonal changes.
Signs: Reluctance to walk, heat in hooves, abnormal gait, and lying down more often.
Causes: Obesity, poor hoof care, high-grain diet, metabolic disorders, or stress from pregnancy.
Prevention: Regular farrier visits, controlled diet, exercise, and weight management.
Treatment: Veterinary hoof care, anti-inflammatory medication, corrective shoeing, and dietary adjustments.
Difficult Birth (Dystocia)
Dystocia occurs when a mare has trouble delivering the foal, which can be life-threatening if not addressed quickly.
Signs: Prolonged labor beyond 20–30 minutes, unusual foal positioning, or extreme distress in the mare.
Causes: Malpresentation of the foal, oversized foal, or uterine weakness.
Prevention: Monitor mares closely during late pregnancy, ensure proper nutrition, and be prepared for foaling with a veterinarian on call.
Treatment: Immediate veterinary intervention, manual repositioning of the foal, or assisted delivery methods.
Retained Placenta After Foaling
After birth, the placenta should pass within 3 hours. Retention beyond this period is a veterinary emergency.
Signs: Placenta hanging from the vulva, foul-smelling discharge, fever, and colic signs.
Causes: Uterine infection, dystocia, poor uterine contractions, or nutritional deficiencies.
Prevention: Proper mare health management, balanced nutrition, and minimizing foaling stress.
Treatment: Veterinary assistance with oxytocin injections, uterine lavage, and antibiotics to prevent infection.
Benefits of Using FarmKeep for Mare Pregnancy Management
Managing a mare’s pregnancy requires organization, close monitoring, and accurate timing. FarmKeep’s livestock breeding software gives you the tools to streamline this process, reduce stress, and improve outcomes for both mare and foal. Here are some key benefits of using FarmKeep for managing mare pregnancies:
Track Heat Cycles and Cover Dates
FarmKeep records and tracks heat cycles so you know the best time for breeding. Accurate cover date tracking ensures you don’t miss a cycle.
Keep Easy Records of Breedings
Instead of scattered notes, FarmKeep stores all breeding details in one place. With a database of 1,200+ animal species and breeds, FarmKeep gives breeders the flexibility to manage not just mares, but their entire herd efficiently.
Spot Pregnancy Signs Early
By logging physical and behavioral changes, FarmKeep helps you identify mare pregnancy signs earlier and with more accuracy.
Monitor Mare Health Week by Week
FarmKeep helps you track your mare’s health, including weight, behavior, and physical changes, while ensuring vaccinations and vet checks are completed on schedule for a safe pregnancy.
Get Foaling Due Date Reminders
The built-in gestation calculator gives you reminders for your mare’s expected foaling date, so you can prepare the foaling stall in advance.
Avoid Missed Heats or Double Coverings
FarmKeep minimizes human error by alerting you to heat cycles, preventing wasted breeding attempts or double coverings.
Share Records with Your Vet Easily
Digital records can be exported or shared directly with your veterinarian. This ensures faster, data-driven care in case of complications.
Save Time on Paperwork
FarmKeep eliminates manual spreadsheets and paperwork. With just a few clicks, you can log updates and access breeding history.
Improve Foal Crop Planning
For breeders, FarmKeep helps organize multiple mares’ cycles, pregnancy stages, and foaling dates to optimize breeding schedules.
Increase Breeding Success Rates
By combining accurate tracking, reminders, and veterinary collaboration, FarmKeep improves the overall success rate of pregnancies and foaling outcomes.
Use FarmKeep’s gestation calculator today to simplify mare pregnancy management and plan your mare’s foaling date with confidence.
What are the earliest signs that my mare might be pregnant?
The earliest signs include missed heat cycles, decreased interest in stallions, and subtle behavioral changes. Veterinary confirmation with a mare pregnancy ultrasound around day 14 is the most reliable method.
How can I use the mare farming app to track pregnancy progress?
You can log breeding dates, health checks, appetite changes, and foaling reminders. Apps like Farmkeep provide automated alerts and keep all records in one place.
When does the mare’s belly start to show pregnancy?
Most mares begin showing a noticeable belly around 6–7 months into gestation. However, body type and nutrition can influence when abdominal enlargement becomes visible.
What behavioral signs indicate that my mare is progressing normally in pregnancy?
Calmness, steady appetite, and lack of heat cycles often indicate normal progress. Irritability, loss of appetite, or unusual aggression should be discussed with your veterinarian.
How do I know when foaling is near using physical signs?
Signs include udder filling, waxing of teats (waxy buildup), softening of the pelvic muscles, and restlessness. These typically occur in the last two to three weeks.
What should I do if my mare starts leaking milk too early?
Early milk leakage can signal placental issues or premature labor. Contact your veterinarian immediately for evaluation.
Can my mare’s appetite change during pregnancy?
Yes. Appetite usually increases during the second and third trimesters as fetal demands grow. A sudden loss of appetite may indicate illness and should be checked.
