Pregnant mares need adequate daily exercise in a paddock or pasture. Any horses kept together should be compatible, which helps to decrease stress. Vaccinations and deworming should be done before the mare is bred, with vaccinations avoided during the first 90 days of gestation. In general, except for rhinopneumonitis and possibly botulism, all vaccinations should be avoided until 30 days before foaling. Thirty days before foaling, the mare should receive vaccinations for Eastern, Western, and West Nile encephalitis, as well as for tetanus.
For the first 7 or 8 months of gestation, the routine diet of pasture or hay and concentrate to maintain good body condition is all that is necessary. Mares that are too thin at foaling will not milk well, and mares that are too fat are subject to developing laminitis or have foaling difficulties.
During the last 3 months of gestation, the mare should be on a gradual, increasing plane of nutrition. The size of the fetus increases substantially during the last trimester, and the mare's weight can be expected to increase. During this time, the mare should be on good-quality legume or grass hay and a concentrate ration of 12%–14% protein. A mare weighing 454–544 kg (1,000–1,200 lb) can be expected to gain 68–90 kg (150–200 lb) during the last trimester with the proper diet. A body condition score of 6.5–7.5 is ideal for most pregnant mares at foaling.
The mare should be checked for the presence of a Caslick's operation of the vulva, which should be opened if present. The foaling process is continuous, with labor divided into three stages. Stage 1 may be 1–4 hours as uterine contractions increase in strength and frequency. Stage 2 is the actual delivery of the foal, which takes 5–15 minutes unless there are complications. Stage 3 is the passage of the fetal membranes, which should occur within a 3-hour period. If the membranes are retained for >3 hours, veterinary treatment is necessary because severe sepsis or laminitis can result.
Some mares may exhibit abdominal pain after foaling, and low-dose analgesics may be helpful. The normal placenta will weigh ~4.5–5.4 kg (10–12 lb) or ~10% of the foal's birth weight, and should be inspected to be sure it has passed entirely.
The mare should be dewormed within 48 hours after foaling to decrease exposure of the foal to parasites. In 90% of foalings, the newborn foal is usually sternal within 1 hour, stands within 2 hours, and nurses within 3 hours. The foaling stall should be at least 4.3 × 4.3 m (14 × 14 ft); a double stall 3.7 × 6.1 m (12 × 20 ft) is more satisfactory. The stall should be bedded with straw or short stem hay. Wood shavings are less desirable because of the possibility of the shavings entering the foal's nostrils or mouth and also contaminating the mare's birth canal. The newborn foal's umbilicus should be dipped in a dilute solution of chlorhexidine (0.5%) or povidone-iodine (1%) several times a day for 2–3 days.
The passage of meconium can be facilitated by use of an enema (warm soapy water, or a commercial sodium-phosphate enema can be administered once). Many foals will not nurse satisfactorily or with vigor until the meconium has passed.
Foals have no immunity at birth and acquire it via ingestion of colostrum. Absorption of colostral antibodies occurs within the first 24 hours of life. Ideally, when ~12 hours old, the foal should have a complete veterinary physical examination, including temperature, heart and lung auscultation, and examination for cleft palate, fractured ribs, or entropion. Evaluation of the foal's IgG concentration is most important. If the foal's serum IgG concentration is < 800 mg/dL, an IV transfusion of plasma is necessary.
Foals should be monitored closely during the first 7 days of life. A healthy foal can become critically ill in a matter of hours. The mare and foal should remain in the box stall for 24–48 hours until the foal is strong enough to follow the mare at a trot or gallop. Then the pair can be turned out in a small area for exercise, which is essential. Haltering and handling the foal during the first week of life will set the stage for the animal's behavior in the future.
Mares that reject their foals usually do so right after birth. This is more common in primiparous mares; they should be monitored carefully to ensure appropriate bonding and safe nursing opportunities for the foal.