Care of Your Pregnant Mare

Breeding your mare and waiting for her foal can be an exciting time for many horse owners! Understanding the changes with your pregnant mare will help you to care for her and her growing foal in utero and optimize her ability to deliver a healthy foal next spring. A mare's average gestation length (pregnancy) is 340 days, divided into early, mid- and late gestation, ) The goal is a successful pregnancy and a healthy foal. To achieve that goal it is critical to start with a healthy mare prior to breeding and address some of the special needs created during pregnancy. It is very important to monitor your mare's attitude, appetite and comfort level closely. If you detect any changes, contact your veterinarian.

Nutrition and Management

Pregnant mares during early to midgestation require little if any special changes to their diet if they are in good body condition. However, during the last 3 months of pregnancy, the foal will gain more than half of its eventual birth weight; therefore, gradually increase your mare's grain and hay rations to meet the increased energy needs of your mare and growing foal in utero. Pregnant mares also drink more water, so place 2 water buckets in her stall and fill them frequently.

Additionally, it is very important to remove the mare from all sources of fescue (pasture or hay) during the last 3 months of gestation. Most fescue contains a fungus (endophyte) that causes prolonged pregnancy, thickening of placental membranes and inhibition of milk production. It can also significantly impact the foal's size and lead to dystocia (difficult foaling) and a sick neonatal foal.

Pregnant mares need adequate exercise, even in late-term pregnancy, unless they have a health problem that does not allow turn out in a pasture. Turning out your mare in a large, flat pasture, so she can graze for a significant period every day is very important to maintain her health and her growing foal's health.

Monitor your mare's attitude, appetite and comfort level closely and also check her udder frequently. If she begins to develop a large udder and drip or stream milk, especially when she is not close to 340 days gestation, often indicates a problem and she should be evaluated by your veterinarian. If she drips or streams milk from her udder and she is around 340 days gestation, it usually indicates that foaling is imminent. However, if she loses too much colostrum (the mare's first milk), she will not have adequate antibodies for her foal and the newborn foal may require treatment such as high quality colostrum from a colostrum bank or a plasma transfusion.

It is ideal to stable the mare in the location where she will foal at least 30 days before foaling, so she has time to produce antibodies specific to her environment. Her stall should be large, so she can easily turn around and lay down if needed. When she is close to foaling, monitoring her closely by a video camera can be very helpful to assess her behavior without intrusion. Mares will often foal at night, when it is quiet and people are not around.

Vaccination and Deworming

Preventive health care measures are important for optimal performance in all horses. Maintaining a current vaccination and deworming schedule for your broodmare is vital to ensure the health of both the mare and foal during pregnancy and after foaling.

Rhinopneumonitis (Rhino) is caused by Equine Herpesvirus type 1 which can cause abortions in pregnant mares (EHV-1). It is recommended to vaccinate broodmares with an inactivated EHV-1 vaccine licensed for prevention of abortion during the fifth, seventh and ninth months of pregnancy. In some instances, your veterinarian may recommend additional vaccination against EHV-1.

Additionally, broodmares should be vaccinated with a killed vaccine containing Eastern and Western Encephalomyelitis, Tetanus, and West Nile Virus four to six weeks prior to foaling. These vaccines are 4 of the 5 core vaccines recommended for broodmares by the American Association of Equine Practitioners (AAEP) vaccination guidelines and are given during late gestation to ensure adequate antibody levels in the mare's colostrum for passive antibody transfer to the foal when the foal nurses on the first day of life. The remaining core vaccine is Rabies which can be administered 4 – 6 weeks prior to foaling or prior to breeding the mare to decrease the vaccinations the mare receives just before foaling.

Parasite control schedules should be based on individual infection status (determined via fecal egg count) and parasite exposure risk assessment. Some dewormers are not approved for use during pregnancy, so it is important to consult your veterinarian who can help you build a safe and effective parasite control strategy for your pregnant mare.

A recommended pregnancy timeline is summarized in the table below.

Month of GestationAction Required
4-6 weeks prior to foaling or prior to breeding the mareRabies vaccination
5th MonthRhinopneumonitis vaccination
7th MonthRhinopneumonitis vaccination
8th MonthRemove fescue from diet
Provide adequate nutritional support to maintain gradual weight gain through late gestation.
9th MonthRhinopneumonitis vaccination
4-6 weeks prior to foalingEastern/Western Encephalomyelitis, Tetanus, and West Nile Vaccination

Monitoring your pregnant mare carefully throughout her gestation and addressing these steps will help you to care for her changing needs and her growing foal in utero, so you can look forward to next spring and arrival of your new foal!