The normal gestation period of mares varies from 320 to 360 days. As a mare approaches parturition, the udder begins to enlarge and may leak small amounts of colostrum, which dries over the ends of the teats, and it is called “waxing”. Other signs of impending (less than 48 hours) parturition include relaxation of the pelvic ligaments and elongation of the vulva. Changes in the composition of the milk (increase of calcium and magnesium concentrations) that occur within the 72 hours pre-foaling, are the basis of commercial kits that help predict foaling.
Understanding the Stages of Parturition in the Mare
Parturition, or labor, occurs in three stages. The first stage of labor is under voluntary control of the mare and is characterized by repositioning of the fetus to a dorsosacral position and initial uterine contractions; it generally lasts a few hours, but it can be interrupted for hours to days. External signs of the first stage of labor include restlessness, sweating, pacing and raising the tail.
The onset of the second stage of labor is the “breaking of the water”, which is the rupture of the chorioallantoic membrane and release of allantoic fluid. Strong uterine contractions result in delivery of the foal, which should be completed within 20 to 40 minutes of the onset of second stage of labor.
The third stage of labor begins after expulsion of the foal and is defined by expulsion of the “after birth” or placenta (aka the fetoplacental membranes). The placenta is generally passed within one hour of expulsion of the foal. Retained placenta (failure to pass fetal membranes within three hours of delivery) is an emergency in mares, and may result in toxic metritis and laminitis. Once the placenta is passed, save the placenta to be inspected by your veterinarian. The placenta should be inspected for completeness and evidence of thickening or infection. Make sure your veterinarian also examines the mare’s reproductive tract for traumatic injury. The mare should also be checked for milk production, udder swelling and signs of mastitis.
Recognizing Normal Equine Maternal-Newborn Relationships
The post-parturient mare starts interacting with her foal by nickering, very soon after birth, even before the foal is completely expelled. The maternal recognition of the newborn foal, called selective bonding, normally starts immediately after delivery and takes up to two to three days. It is normal for the post-parturient mare to be protective of her foal and keep herself between the baby and any perceived threat, including people and other horses the mare is otherwise familiar with.
The mare may act aggressive for one to two days. Even a mare that normally has “good-manners” towards people may act aggressively. Close confinement often aggravates this behavior. This can be easily avoided if the pair is kept in a large space.
Another important thing to remember is that “milk letdown” produces a transient discomfort to which the mare may react. Once the mare has relaxed, and with repetitive nursing, this response disappears.
Identifying Abnormal Mothering Behavior
Overall, mares have excellent maternal skills. Inadequate mothering behavior is uncommon, and estimated to occur in less than five percent of the parturitions. It occurs especially in first-time mothers, and it often becomes apparent soon after birth, however the abnormal behavior may take a few days to be manifested. It is thought that true “poor mothering” behavior may have a genetic predisposition.
The five most common abnormal mothering behaviors are:
- Absence of bonding
- Fear of the newborn foal
- Reluctance of nursing
- True foal rejection
Absence of bonding and lack of protective behavior is generally seen when either the mare or the foal is sick or is receiving medication. It is also relatively common if the foal delivery involved a lot of manipulation such as in difficult births (called dystocias) or after cesarian section.
Fear of the newborn foal occurs when the mare does not recognize the foal as her own baby. Instead of the normal bonding behavior, the mare tries to get away from her own foal, as if it is an intruder. The mare will eventually acclimate to her foal, but may not bond very well to this foal. This behavior occurs more commonly in the first time mothers, and it is unlikely to be repeated in subsequent pregnancies.
Overprotection is defined as aggressively protecting the foal, to the point of being a dangerous not only to the people handling the mare but also to the foal. While rushing to get herself in front of her foal to protect it from a perceived threat, the mare may injure the baby by stepping on or crushing her own foal. Although the mare may appear to injure the foal, overprotection is quite distinct from deliberate attacks on the foal that occur with true rejection.
The reluctance of nursing is probably the most common problem, and it should also be differentiated from deliberate attacks on the foal. It is possible that the discomfort associated with “milk letdown” causes the mare to overreact. Alternatively, the mare may be reluctant to have the foal nurse because she is “touchy” about her udder, especially if there is edema. If a mare is “touchy”, her udder should be handled regularly prior and throughout the following pregnancies.
True foal rejection is a very serious inadequate mothering behavior, and fortunately it is the least common. The reason why some mares truly reject their foals remains unknown. It is thought that this behavior is more likely to reoccur again in subsequent pregnancies than the other abnormal maternal behaviors. The mare becomes aggressive toward her baby and often savagely attacks the foal. The mare may bite, lift and toss the foal, or corner and stomp on it. Once you have confirmed that the mare is truly rejecting and attacking her foal, they need to be separated permanently.
Abnormal maternal-newborn interaction may predispose to serious neonatal illness. Can you avoid them? How? There are a few things you can do to avoid the abnormal maternal newborn interactions mentioned above. You should handle the mare throughout her pregnancy and after foaling, cautiously but consistently. You should avoid too much commotion around the mare and her newborn, and avoid confinement in a small space. It is important to allow enough space, especially to the extremely protective mares. The mare should be allowed to bond to foal without interference. You should avoid handling the foal excessively, but try to handle the foal a little and consistently. Always make sure the foal has received adequate amount of good quality colostrum and check for adequate passive transfer of maternal immunity (see below). Remember to be observant and deal with any problem as soon as possible.
Anticipating and Identifying the Problematic or High-Risk Newborn Foal
In order to ensure the best chance of you not losing your mare’s foal due to neonatal diseases it is important to be able to anticipate and identify the risk factors associated with the most common problems of newborn foals. The three most common problems of the newborn foal are failure of passive transfer of maternal immunity, neonatal sepsis (generalized bacterial infection) and prolonged birth asphyxia. They result in a number of serious, and often life-threatening, conditions. In fact, most disorders of the newborn result from high-risk pregnancies. Therefore, any condition that affects fetal development and maturity, delivery and the peripartum period may result in severe neonatal illness.
The factors associated with high-risk newborn foals and problems during the neonatal period can be divided into those associated with environmental conditions, maternal (mare) factors, delivery and fetal (foal) factors. Certain environmental conditions predispose to neonatal illnesses, including unsanitary conditions, poor husbandry, exposure to new pathogens against which the mare has no immunity, and extreme environmental temperatures. If you are planning to send your mare to foal “out” somewhere else so she can be bred on the foal heat, make sure to evaluate the farm’s environmental conditions carefully.
The list of maternal, delivery and fetal factors predisposing to neonatal illnesses is quite lengthy. The age and the health status of the pregnant mare, any illness she may have and even prolonged transportation can have an important impact on her pregnancy and delivery. Uterine problems such as placental inflammation or infection, also called placentitis, as well as twin pregnancy can affect the delivery of nutrients to the fetus altering its’ development. In case of infectious placentitis, the fetus is exposed to the infectious agent while inside the uterus, leading to likely neonatal sepsis. Moreover, any parturition problems such as dystocias, “red bag” (or premature placental separation) often result in prolonged birth asphyxia.
The absence of or low production of colostrum, or loss of colostrum in mares that drip milk prior to foaling, will result in failure of passive transfer of immunity and predispose the foal to neonatal septicemia. Incomplete fetal development due to premature delivery (less than 320 days of gestation) or delayed growth of the fetus, which results in immaturity, are often associated with a number of neonatal problems, especially involving their lungs and bones. The foal may fail to adequately ingest colostrum, not only because of inadequate availability of maternal colostrum, but also due to an inability to stand in case of abnormalities of the limbs or neurologic problems (“dummy foal”), as well as the inability to swallow.
How Can You Tell if the Foal is Healthy?
A healthy newborn foal is strong, responsive and very active. A number of things should be noted when you observe the newborn from a distance including the foal’s attitude, willingness to nurse, awareness of the surroundings, the relationship with the mare, the ability to move around and the respiratory pattern. We all have heard that the foal is one of the most precocious newborns in the animal kingdom. In fact, the newborn foal is very active soon after birth and is able to keep up with its dam.
Mares encourage their newborn foals to get up and nurse within the first hour after birth. We Often Refer To The “1-2-3 RULE” Of The Newborn Foal:
- A healthy foal should stand within 1 hour
- Should start nursing within 2 hours
- Should pass the meconium (first feces) within 3 hours after birth
It is important for the foal to ingest the colostrum as soon as possible after standing. The suckle reflex begins at approximately 20 minutes after birth, and becomes stronger and stronger with time. Normal foals nurse every 30 minutes, and failure to suckle is the first sign of a neonatal problem. It is advisable to have a routine evaluation of newborn foal by your veterinarian within 12 to 24 hours of birth. This should include careful observation and physical examination, and assessment of maturity and passive transfer of maternal immunity.
If the newborn foal does not stand and nurse by two hours after birth, you should consider it abnormal, and you should consult your veterinarian as soon as possible. It is important to remember that a high-risk newborn foal may look relatively normal for several hours after birth. In order to be able to identify early signs of a neonatal problem such as neonatal sepsis, it is important to answer a few questions about the foal including:
- Has the foal been getting up and nursing? How often?
- Have you checked the udder?
- Does the foal still appear hungry? Check the mare’s udder for fullness before and after the foal has nursed and check to see if milk is coming out of the foal’s nostrils.
- Has the foal passed the meconium?
- Have you given the foal an enema? More than one!
The first feces of the newborn (called meconium) are dark brown and either pasty or firm little fecal balls. It is important for the foal to pass the meconium within 3 hours after birth and the best way to stimulate gut movement and passage of the meconium is nursing properly. You may be inclined to give the foal an enema right away, however, this is generally not necessary. But, one enema, if given carefully, is unlikely to harm the foal. However, you must not get carried away with enemas to the newborn foal! Too many enemas can be harmful. If the foal continues to strain to defecate without success, you should contact your veterinarian.
What are Some of the Signs of Abnormalities?
Signs of problems include not nursing often (make sure to check the udder), salivating excessively, grinding teeth, or showing signs of abdominal distension and pain (such as getting up and down, rolling on his back). Other signs include straining to defecate and urinate, limb abnormalities such as angular or flexural limb deformities and lameness.
Care of the Newborn Foal
Well-being checkup of the newborn foal and a post-foaling check on the mare are very important. It is advisable to have your veterinarian check the newborn foal and the mare even if they look pretty good! Remember to save the placenta to be inspected by your veterinarian. Make sure the foal’s blood is always checked for adequate transfer of maternal immunity.
Appropriate Passive Transfer of Maternal Immunity
The neonatal foal is immunologically competent (able to mount an immune response) at birth. However, their naïve immune system is very inefficient to fight invasion of infectious organisms, including bacteria, fungus, virus and parasites. Passive transfer of maternal antibodies via colostrum is the principal immunological protection in the newborn foal. Failure of passive transfer of maternal immunoglobulins can occur with failure or delay to suckle, failure of the dam to produce good quality colostrum, and leakage of colostrum prior to parturition, and it is the single most important predisposing factor for development of life-threatening neonatal septicemia.
Good quality colostrum should be creamy, yellow and sticky. If inadequate passive transfer occurs, the foal should receive supplemental colostrum as soon as possible. Colostrum is the preferable source of passive immunity for the newborn foal because colostrum contains not only immunoglobulins (antibodies against microorganisms) but other important factors.
The timing for oral administration of colostrum, or its substitute, is critical. If more than six to eight hours have elapsed since birth, adequate intestinal absorption of enterally administered colostrum is unlikely, and the intravenous administration of plasma will be required to provide passive transfer of immunoglobulins to the newborn foal. Therefore, if you suspect the foal is not getting adequate colostrum, contact your veterinarian about providing a substitute as soon as possible.
Evaluation of passive transfer of colostral antibodies in the foal’s blood should always be performed. It can be done as early as eight hours, but it is normally done between 12 to 24 hours after birth. Assuming the foal is normal and has nursed within two hours of birth, the foal’s blood should have a certain level of immunoglobulins by eight hours. If the level is not adequate, early detection of failure of passive transfer allows administration of colostrum (immunoglobulin supplementation) within an optimal window of time.
Later assessment of the immunoglobulin level better represents the ultimate status of passive transfer of immunity, since maximum concentrations occurs between 12 to 24 hours after birth.
Support of the Newborn Foal
Normally, foals suckle approximately 30 times per day, ingesting 12 to 20 percent of their body weight in milk, and gaining an average of 2 to 3% of their body weight daily (for an average size foal of 100 lbs., the foal should gain two to three pounds per day). Adequate nutritional support is of paramount importance for the newborn. If the newborn foal is unable to nurse, alternative routes of nutritional support are necessary.
Do not forget the main rule when feeding foals: “Avoid aspiration pneumonia!!” Do not “jug”, syringe-feed or force-feed the foal. These methods of feeding are likely to result in aspiration of the milk into the lungs. Even bottle-feeding, if not done properly, can result in aspiration. If the foal is not nursing, contact your veterinarian as soon as possible. Once the cause of inappropriate nutrition is established you and your veterinarian can make a plan about how to provide the appropriate nutrition to the newborn foal. Your veterinarian may place a small diameter, pliable nasogastric or nasoesophageal feeding tube. Always make sure the foal is standing when being fed, even when you are feeding via feeding tube. If the foal is lying down, the overflow can back up into the throat (pharynx) and then be aspirated into the lungs.
The mare should be hand-milked every two hours, and the mare’s milk administered to the foal. If the mare does not produce sufficient milk to meet the nutritional requirements of the foal, a number of brands of good quality equine milk replacer are available. Other alternatives include fresh (non-evaporated) goat’s milk, which is a fairly good substitute to mare’s milk. Cow’s milk should only be used as last option and it should be modified by the addition of supplemental calcium and dextrose. Calf milk replacers should be avoided.
If your foal is sick and has become unable to rise (recumbent), there are a few things you can do to help stabilize the newborn foal while awaiting veterinary assistance, including preventing hypothermia and keeping the foal lying in upright (sternal) position. When you try to keep the foal warm, be cautious to avoid over-heating of the foal with electric blankets and heaters. Over-heating can aggravate circulatory problems. Keeping the foal in sternal position, rather than lying on its side, helps the foal to breathe more efficiently, which is extremely important in any sick foal.
Courtesy of AAEP
By L.R.R. Costa, MV, MS, DACVIM