During the last trimester, pregnant mares should be on a slowly rising plane of nutrition that includes a concentrate containing at least 12–14% protein. The diet should be balanced in calcium, phosphorus, copper, and zinc. During the immediate prepartum period, bran or psyllium can be added to the diet as a laxative to keep feces soft and to reduce the risk of postpartum impactions.

In addition to routine deworming throughout pregnancy, mares should be dewormed within 24–48 hr of parturition to reduce the foal's exposure to parasite ova in the milk as well as in the manure. Mares should receive annual booster vaccinations 4–6 wk prepartum to improve colostral quality. In addition to producing antibodies in response to vaccination, mares produce antibodies to pathogens indigenous to their environment. Because colostrum is produced during the last 3–5 wk of pregnancy, mares should not be moved to new premises during the immediate prepartum period, and mares and foals should remain in the foaling environment during the early postnatal period.

Before parturition, the mare's udder and perineum should be cleaned and fresh bedding added to the stall to optimize the hygiene of the foaling environment and reduce the neonate's exposure to bacterial pathogens before colostrum ingestion. Ideally, the flooring in the foaling stall should be easy to disinfect. Immediately after birth, the foal's umbilicus should be dipped with either 2% iodine or chlorhexidine disinfectant to decrease the risk of ascending umbilical remnant infection and septicemia. A gravity enema is often administered prophylactically to stimulate meconium passage and reduce the likelihood of meconium impaction. Early colostrum ingestion is essential to ensure adequate absorption of colostral antibodies and to stimulate early gut closure and reduce uptake of potentially pathogenic bacteria via translocation across the intestinal mucosa. (Also see Management of the Neonate.)

Foals are born virtually without gamma globulins and rely on passive immunity through absorption of colostral antibodies for protection against common equine infectious diseases during the first 4–8 wk of life. Intestinal absorption of colostral antibodies is optimal during the first 10 hr of life and ceases after 24 hr. A newborn foal's serum IgG concentration should be >800 mg/dL after colostrum ingestion. Foals with <400 mg/dL of serum IgG should be supplemented with additional colostrum if <18–20 hr old, or given a plasma transfusion if >20 hr old or if compromised GI function is suspected.

In general, foaling mares should be kept in an environment where they can be monitored frequently both before and after foaling. Attended foalings are mandatory to help avoid foal loss due to correctable periparturient problems (eg, dystocia, failure to rupture fetal membranes normally, and maternal rejection or aggression).

Also see Nutrition: Horses: Feeding the Aged Horse and the Orphan Foal.

Last full review/revision July 2011 by Wendy E. Vaala, VMD, DACVIM