Pregnant mares need adequate daily exercise in a paddock or pasture, and any horses kept together should be compatible, which helps to reduce stress. Vaccinations and deworming should be done before the mare is bred, with no vaccinations given 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 mo of gestation, the routine diet of pasture or hay and concentrate to maintain good body condition is all that is necessary. Mares too thin at foaling will not milk well, and mares too fat are subject to developing laminitis or have foaling difficulties. During the last 3 mo of gestation, the mare should be on a gradual, increasing plane of nutrition. The size of the fetus increases significantly 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 1,000–1,200 pounds (454–544 kg) can be expected to gain 150–200 pounds 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 hr as uterine contractions increase in strength and frequency. Stage 2 is the actual delivery of the foal, which takes 5–15 min unless there are complications. Stage 3 is the passage of the fetal membranes, which should occur within a 3-hr period. If the membranes are retained for >3 hr, then 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 ~10–12 pounds (4.5–5.4 kg) or ~10% of the foal's birth weight.
The mare should be dewormed within 48 hr after foaling to reduce exposure of the foal to parasites. In 90% of foalings, the newborn foal is usually sternal within 1 hr, stands within 2 hr, and nurses within 3 hr. The foaling stall should be at least 14 × 14 feet (4.3 × 4.3 m); a double stall 12 × 20 feet (3.7 × 6.1 m) 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 used once). Many foals will not nurse satisfactorily or with vigor until the meconium has passed.
Foals have no immunity at birth and acquire it through ingestion of colostrum. Absorption of colostral antibodies occurs within the first 24 hr of life. Ideally, when ~12 hr 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 level is most important. If the foal's serum level 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 hr 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 and requires intense supervision.