Equine Health Library


Growth & Development

Growth & Development | Other Concerns


A healthy newborn foal should be able to sit sternal with a suckle reflex within 10 to 20 minutes of delivery, stand within one hour and should be nursing within two hours.

Newborn Care

If your foal is too weak to stand and nurse, contact your veterinarian immediately. Early veterinary intervention can be lifesaving. When it comes to your newborn foal, a “wait and see” attitude can be dangerous, since compromised foals can deteriorate within hours. Err on the side of caution and call your veterinarian if your foal deviates from this normal timeline.

Foals should be able to sit upright in a sternal position within 10 to 20 minutes after birth.

ParameterNormal Observation
Temperature99°F to 102°F
Heart Rate80 to 100 beats/minute
Breathing rate at rest20 to 40 breaths/minute
MeconiumPassage completed by 12 to 24 hours of age
Nursing frequencyAverage of 3 to 7 times/hour
Placental weight10 to 11 percent of foal’s birth weight
Birth weight and height10 percent of mature weight
60 percent of mature height

Growth Stages

Your foal is changing faster than the blink of an eye. One day, he is all gangly and awkward; the next, he seems to have grown into his legs with grace. As exciting as it is to watch your foal transform, it’s also important to pay attention to key milestones along the way.

AgeChanges to Watch For
2 days to 2 weeksNurses six to 10 times per hour. Listlessness and decreasing nursing vigor are early signs of illness.
2 weeks to 2 monthsSigns of diarrhea or respiratory disease.
2 months to 4 monthsHigh incidence of respiratory disease and diarrhea in this age group. Infectious causes are variable and include a variety of bacteria, viruses and/or parasites.

It’s easy to see why early care is so important to the long-term health of your foal. By the time he is six months old, your foal will have already attained about 80 percent of his mature height and half of his mature weight.

To track your foal’s growth, use our Equine Health Library Foal Growth Chart to compare you foal’s growth to the recommended growth rate for its age and breed. Print out a copy, and then mark an “X” at the appropriate weight-age intersection on the growth chart every time you weigh your foal. Small or newborn foals can be weighed on a bathroom scale. Weight tapes can be used to estimate the weight of older foals when scales are not available.

Of course, if you have concerns, call your veterinarian. Early intervention can be the key to long-term good health.

First Two Weeks

When your foal is born, he weighs approximately 10 percent of his mature weight and is about 60 percent of his mature height. Your newborn foal’s temperature should be 99 to 102 degrees Fahrenheit, heartrate should be 80 to100 beats per minute, and respiratory rate should be 30 to 40 breaths per minute. You should monitor all of these vital signs to make sure your newborn foal is not getting sick.

Changes in a foal’s first two weeks

  • First deciduous incisors (centrals) present at birth or by the first week of age
  • First, second and third deciduous premolars erupt by two weeks of age
  • Your foal should nurse six to 10 times per hour. Listlessness and decreasing nursing vigor are early signs of illness
  • Make sure to monitor/reduce any umbilical or inguinal hernias.

Vital signs during the first two weeks

  • 99 to 102 degrees Fahrenheit
  • 70 to 80 heartbeats per minute
  • 23 to 30 breaths per minute

Always obtain vital signs when your foal is quiet and resting since exercise and/or excitement can falsely elevate most values. If your foal’s vital signs are consistently abnormal, contact your veterinarian.

Most foals experience a bout of self-limiting diarrhea within the first 7-14 days of life, often called “foal heat” diarrhea. The cause is usually a change in the foal’s diet coupled with normal physiologic changes in the bacteria colonizing the foal’s intestines. If it persists or you are worried, contact your veterinarian.

Two Weeks to Two Months

Here are the most important physical changes to track in your foal between 2 weeks and 2 months of age.

  • Testicles should have descended in most colts by this time
  • Second deciduous incisors (intermediates) erupt at 4 to 6 weeks of age

Vital signs two weeks to two months

  • 99 to 102 degrees Fahrenheit
  • 60 to 70 heartbeats per minute
  • 20 to 30 breaths per minute

Always obtain vital signs when your foal is quiet and resting since exercise and/or excitement can falsely elevate most values. If your foal’s vital signs are consistently abnormal, contact your veterinarian.

Two to Four Months

Physical Changes

  • High incidence of respiratory disease and diarrhea in this age group:
    • Signs of respiratory disease can be mild or unmistakable. Subtle, non-specific signs include increased breathing rate or effort of breathing when lying down at rest and prolonged recovery rate after exercise. Most noticeable signs include a cough (listen to your foals after exercise) and nasal discharge that can be clear or cloudy and purulent. At the first signs of respiratory disease, take your foal’s temperature and call your veterinarian.
    • Early signs of intestinal disease that often precede the onset of diarrhea include low-grade colic, loss of appetite, listless behavior and perhaps distention of the abdomen with fluid and/or gas. Diarrhea can vary in consistency from “cow pie” to watery and projectile in character. Bloody or tarry diarrhea is a sign of severe bacterial infection, often the result of either Salmonella or Clostridia infection. Consult with your veterinarian at the first signs of diarrhea. While some bouts of diarrhea can be mild and self-limiting, others can be highly contagious and/or potentially fatal for your foal. The younger the foal, the more susceptible they are too rapid dehydration and electrolyte imbalances associated with watery diarrhea.
  • Infectious causes are variable and include a variety of bacteria, viruses and/or parasites.
  • Severe carpal deformities require correction by three to four months. Carpal valgus is the most common deformity affecting the carpus (knee) and results in a “base wide” stance.

Vital signs two to four months

  • 99 to 101.5 degrees Fahrenheit
  • 60 to 70 heartbeats per minute
  • 20 to 30 breaths per minute

Always obtain vital signs when your foal is quiet and resting since exercise and/or excitement can falsely elevate most values. If your foal’s vital signs are consistently abnormal, contact your veterinarian.

Four to Six Months

Physical Changes

  • Wolf teeth (first permanent premolars) erupt at 5 to 6 months of age
  • All hernias (e.g., umbilical, inguinal) should have resolved
  • All carpal deformities should be corrected by 6 months of age
  • Weaning occurs for most foals. Learn more on feeding a weanling
  • Monitor for physitis and acquired angular deformities and other signs of developmental orthopedic diseases (DOD)

Six Months to One Year

Physical Changes

  • At 6 months, most foals have reached 50 percent of mature weight and 80 percent of mature height
  • Third deciduous incisors (corners) erupt at 6 to 9 months of age
  • First molars (fourth cheek teeth) erupt between 9 and 12 months of age
  • Make sure to separate fillies and colts in order to prevent pregnancies

Never hesitate to contact your veterinarian if you are concerned about your foal’s overall health and appearance, conformational changes, appetite, growth rate or if you have questions about vaccinations, deworming or nutrition.

Umbilical stump

Dip your foal’s umbilical stump with dilute chlorhexidine or iodine twice daily for two to three days or until the stump is dry. During the first week, check the umbilicus daily for signs of swelling, tenderness or discharge, which are typically associated with infection.

Every foal should urinate within eight to 10 hours of delivery. Observe urination to be certain there is no urine leaking from the umbilicus. This condition is known as a patent urachus and is abnormal.

Prematurity and Related Conditions

Underdevelopment or immaturity can happen two ways: A shortened gestation length ending in premature delivery (gestation length less than 320 days) or an abnormal intrauterine environment that failed to provide sufficient nutrition to the fetus.


Signs of immaturity associated with shortened gestation length (less than 320 days)

  • Small body size
  • Domed forehead
  • Silky hair coat
  • Floppy ears
  • Generalized weakness
  • Respiratory distress (rapid breathing, labored breathing with nostril flare)
  • Difficulty maintaining a normal body temperature
  • Tendon/joint laxity

Affected foals may be too weak to stand without assistance and, when they do stand, place most of their weight on the backs of pasterns or heel bulbs rather than on their hooves. Radiographs often reveal that many of the bones in the foal’s hocks, fetlocks and knees (carpi) are not fully calcified. Premature foals may have difficulty maintaining a normal body temperature, blood pressure and blood glucose concentration. Some premature foals are unable to ingest and digest mare’s milk adequately and often require intravenous nutritional support. Some “preemies” require oxygen therapy to support lung function.

Premature foal: small, thin foal with a finer than normal hair coat. Other physical signs of prematurity include joint and tendon laxity, generalized weakness, and incompletely ossified (calcified) bones in the hocks, carpi and fetlocks.


Signs of immaturity due to disturbed in-utero development/uteroplacental disease include many of the same signs described above. The affected foal may not be smaller in stature than a full-term foal but is often thin and underweight. Dysmature foals can have many “premature” characteristics, including generalized weakness, incomplete calcification of the small bones in the hocks and carpi, and laxity of tendons and joints. Dysmature foals may be called “small for gestational age” or “growth retarded.”

Post maturity

Signs of immaturity associated with a longer-than-normal gestation length

  • Small or normal stature; often underweight and thin
  • Metabolic instability: Unable to maintain normal blood concentrations of glucose and other electrolytes
  • Difficulty maintaining normal blood pressure
  • Inability to absorb adequate amounts of antibody from colostrum
  • Incomplete ossification of bones in some individuals

Common abnormalities detected in blood work from immature and premature foals include low white blood cell count, low blood glucose (sugar) levels and low oxygen levels in arterial blood samples.


  • Fluid and nutritional support if the foal is unable to nurse normally
  • Respiratory support: Intranasal oxygen; oral caffeine if respiratory depression is present; positive pressure ventilation for severe respiratory compromise
  • Immune support: Colostrum; intravenous plasma containing high levels of antibodies; prophylactic antibiotic therapy
  • Musculoskeletal support: Radiographs of the hocks and knees are essential to evaluate the degree of bone ossification. Conservative exercise on soft footing should be encouraged to improve tendon and periarticular laxity (e.g., wobbly hocks, knees and fetlocks due to weak ligaments surrounding the joints). Special glue-on shoes that include heel extensions can be fashioned to help correct tendon laxity. Excessive exercise should be avoided to prevent damage to the developing bones

Jaundice foal syndrome (Neonatal Isoerythrolysis)

Neonatal Isoerythrolysis (NI), also known as “jaundice foal syndrome,” is caused by blood type incompatibility between sire and dam. The foal inherits the sire’s blood type (usually type Aa or Qa), and the mare produces antibodies against that blood type. Those antibodies are concentrated in her colostrum, which, when absorbed by the foal during nursing, attack and destroy the foal’s red blood cells.

Signs of NI

  • Progressive jaundice manifested by yellow discoloration of the gums and whites of the eyes.
  • Anemia.
  • Hemoglobinuria as evidenced by red, discolored urine.
  • Progressive weakness.

Therapy includes blood transfusions if the anemia becomes severe. Good nursing care also is important. Although the affected foal should not receive his dam’s colostrum, another “safe” source of colostrum should be provided. The mare must be hand-milked to remove all of her colostrum – typically this requires milking the mare for at least 24 hours and discarding that colostrum.

Mares that have had one NI foal will be at increased risk to have a second one in the future, especially if they are bred back to the same stallion. Talk with your veterinarian about blood tests during late pregnancy to determine if your mare is carrying another potential NI foal.

If you know ahead of time that her foal is an NI candidate, you can be certain that the foal receives colostrum from a mare other than its own mother. Foals will need to be muzzled during the first 24 hours of life and provided with a safe source of colostrum. During this time, the mare will need to be stripped of her colostrum. Once the colostrum is gone, her milk will be safe for her foal to nurse.

Uroperitoneum (ruptured bladder)

Foals may be born with a ruptured bladder or may acquire it through trauma or infection after birth. The congenital form occurs due to failure of the dorsal wall of the bladder to close during development in utero. More commonly, the bladder ruptures during a difficult delivery. This form occurs most often in colts.

After delivery, foals of either sex also can experience bladder or urachal rupture secondary to infection of the umbilical arteries and/or urachus, or of the bladder wall. Critically ill, recumbent foals may rupture their bladders while being lifted and turned with a full bladder or from chronic over-distension associated with their generalized disease state. Foals suffering from botulism also can rupture their bladder secondary to lack of bladder tone and chronic over-distention.

Clinical signs

  • Stretching out and straining to urinate
  • Mild colic
  • Loss of suckle reflex/desire
  • Slowly increasing abdominal distention due to accumulation of urine within the abdominal cavity
  • Heartbeat irregularities due to electrolyte imbalances associated with bladder rupture

Diagnosis and treatment

A diagnosis of uroperitoneum can be made quickly using transabdominal ultrasound to visualize large volumes of free fluid within the abdomen and a small, irregularly shaped, collapsed bladder. Loops of bowel are observed floating within the fluids.

Foals with ruptured bladders will have very abnormal electrolyte values – low sodium and chloride concentrations and high potassium concentrations – that can cause serious heartbeat arrhythmias. Creatinine (a marker of kidney disease) concentration begins to increase in the blood.

Definitive treatment involves surgical repair of the bladder and resection (removal) of the umbilical remnants. Prior to surgery, urine within the abdomen should be drained and the electrolyte imbalances should be corrected using appropriate intravenous fluid therapy.

Genetic diseases

Even when you carefully plan your mare’s pregnancy, some foals may be born with inherited or genetic diseases that can jeopardize their survival.

Autosomal dominant trait: Carriers (heterozygotes) are symptomatic (show clinical signs). Only one parent may be a carrier of the trait.

Autosomal recessive trait: Carriers are often asymptomatic (do not show clinical signs). Birth of an affected (homozygous) foal means that both parents are carriers of the trait.

Hyperkalemic Periodic Paralysis (HYPP)

First recognized in the early 1980s in descendants from the popular halter champion “Impressive,” HYPP affects an estimated 4 percent of all Quarter Horses. Related breeds such as Paints and Appaloosas can also be affected if they are Impressive-bred. The American Quarter Horse Association will no longer register foals born in 2007 or later that are homozygotes for HYPP. A single-gene mutation is responsible for the condition. Homozygotes (H/H) are more severely affected, and heterozygotes (N/H, carriers) have variable signs.

Clinical signs

  • Uncontrollable muscle twitching
  • Profound muscle weakness that can result in an inability to rise
  • Laryngeal paralysis resulting difficulty breathing
  • Difficulty in regulating potassium concentrations in muscle cells and in the blood stream

Glycogen Branching Enzyme Deficiency (GBED)

First identified at the University of Minnesota, GBED affects Quarter Horses, QH-crosses and QH-related breeds. This genetic mutation may be present in up to 10 percent of Quarter Horses and American Paint Horses.

Clinical signs

  • Late term abortion or stillbirth. Three percent of abortions in Quarter Horses may be due to GBED
  • Weakness and low body temperature at birth
  • Initially foals appear healthy and then begin to fade
  • Seizures
  • Sudden death due to cardiac arrest
  • Contracted tendons in all four limbs
  • Respiratory distress, breathing difficulty due to muscle fatigue
  • All affected foals succumb to this condition within the first few days of life

Overo Lethal White Syndrome (OLWS)

This condition affects all-white foals in Quarter Horses, Paints, American Miniature Horses and Arabians. Foals with this syndrome lack normal nerve innervation of their intestinal tract, resulting in absence of normal gut motility. This is a fatal condition; there is no surgical correction available. Newborn foals are unable to pass meconium and present with colic within the first 24 to 48 hours of life.

Testable Equine Genetic Diseases

To avoid genetic diseases, test your mare and stallion before breeding. All of these conditions have the potential to be treated successfully depending on how severely affected the foal is and how early the abnormality is recognized.

ConditionAffected BreedsMaterial Required For Test
Hyperkalemic Periodic Paralysis (HYPP)QH, PaintHair
Hereditary Equine Regional Dermal Asthenia (HERDA)QH, PaintHair
Polysaccharide Storage Myopathy (PSSM)QH, Paint, TB, DraftBlood, hair
Overo Lethal White Syndrome (OLWS)Arabian and Arabian crossesBlood, oral swab
Cerebellar abiotrophyPaint, QH, TB, Arabian, American MiniatureHair
Glycogen Branching Enzyme Deficiency (GBED)ArabianHair
Junctional Epidermolysis Bullosa (JEB)QH, QH-related breeds and crossesHair
Lavender Foal SyndromeBelgian, American SaddlebredHair
Congenital Stationary, Night BlindnessAppaloosa, Miniature Horse, and other breedsHair

Additional information about genetic diseases and testing: