Feeding and Managing Pregnant Mares: Prenatal Nutrition

Pregnant MareMany broodmares are in the last half of gestation at this time. The latter part of gestation is one of the most important development periods in the life of a foal when the foal is developing in the uterus of the mare.  The importance of this period was recognized in the Nutrient Requirements of Horses, Sixth Edition, when the Committee established that the nutrient requirements of the mare start increasing at the 6th month of gestation, earlier than previously believed.  During the last three months of gestation, the foal may be gaining an average of one pound per day.

The key elements of managing the pregnant mare are the following:

  • Maintain appropriate body condition score.
    • Mares should be at about a body condition score 6 when they foal so that they have sufficient energy reserves for early lactation as well as to maintain condition for re-breeding.
  • Adequate protein/amino acid intake.
    • Lysine, methionine, and threonine, the first 3 limiting essential amino acids, need to sufficient in the diet for placental and fetal development.
  • Adequate mineral and trace mineral intake.
    • The mare needs to be receiving adequate calcium, phosphorus, magnesium, copper, zinc, manganese and selenium to provide minerals for the development of the foal and to build the foals own trace mineral reserves.  Trace minerals are also critical for immune support.
  • Vaccinations and deworming.
    • A regular vaccination program should be developed in conjunction with a veterinarian so the mare is protected herself and can also produce the appropriate antibodies to protect the foal when it nurses and receives the colostrum that contains maternal antibodies.  This is what protects the foal until it can be vaccinated and develop its own antibodies.  The mare should also be dewormed as needed prior to foaling.

Good quality pasture or forage may provide sufficient energy thru late gestation, but may NOT provide adequate amino acids and minerals for optimal fetal development.  A well-designed ration balancer product may be used from month 5 to about month 10 or 11 of gestation to provide the missing nutrients.  A well-designed feed for broodmares and foals should be introduced prior to foaling so that the mare is on the feed before she foals to avoid the need for a sudden change in feed at foaling. This feed can then be increased after foaling to provide both the increased energy and the increased nutrients that are required for lactation, as well as providing nutrition for the foal when it starts to nibble on feed.  Fresh clean water and free choice salt should also be available at all times.

Feeding the broodmare properly can help reduce the risk of developmental problems for the foal and help insure that the mare can be rebred in a timely manner to produce another foal the following year if desired.

Feeding the Broodmare During Lactation

Proper nutrition for the broodmare during lactation is essential to make certain that she produces adequate milk for the foal and also maintains her body condition so that she will re-breed successfully and safely carry the next year’s foal.

The broodmare has substantial increases in requirements for digestible energy, protein, lysine and minerals as she goes from the last month of gestation to the first month of lactation. For an 1100 lb mare, the following changes occur:

  • Her DE requirement goes from 21.4 Mcal per day to 31.7 Mcal per day
  • Her protein requirement goes from 630 grams to 1535 grams per day
  • Her lysine requirement goes from 27.1 grams to 84.8 grams per day
  • Her calcium requirement goes from 20 grams per day to 59.1 grams per day
  • Similar increases occur in other amino acids and minerals, as well. They are documented in the Nutrient Requirements of Horses, Sixth Edition, pages 298-299.

If her feed intake is not increased to provide these nutrients, she will maintain milk product by using her body stores for energy, amino acids and minerals, causing loss of weight and loss of body condition as well as mineral losses.

Foal scratching face

Ferris with mom Rosie - foals exhibit the most entertaining behaviors....

To meet her increased DE requirement, an additional 7.5 pounds of grain containing 1364 Calories/lb will need to be added to her diet gradually post foaling. Fortunately, she also can consume more dry matter during lactation, so she is actually able to eat more forage and more feed. If she is fed a product suitable for lactating mares, the additional feed will provide the additional energy as well as the other important nutrients. She will also require unlimited access to water and salt free choice along with good quality forage.

If she continues to lose weight, she is much less likely to cycle normally during lactation and less likely to become pregnant and carry the next foal. This may be why some mares are “every other year” mares in producing foals. They are frequently mares that produce large foals and milk very heavy during lactation. As a result, they do not maintain body condition and do not re-breed and carry a foal the next year. When they are not in foal and not lactating, they gain weight and come back into the next breeding season in good flesh and breed successfully. This is even more likely if they are not in a suitable body condition (BCS 6+) prior to foaling.

The nutrient requirements of the mare will start to decrease at the 3rd month of lactation and will gradually decrease until the foal is weaned. Monitoring body condition of the mare and the foal is one of the best ways to determine if the feeding program for both is producing the desired results!

Feeding Broodmares

During a mare’s pregnancy, some significant changes happen that cause her nutrition needs to skyrocket. While bred mares should be fed a quality maintenance diet for the first half of their pregnancy, a maintenance feeding program just won’t cut it after the mid-way point of the pregnancy.

Since we cannot increase the feed intake drastically when the mare foals, she needs to be carrying some extra fat stores so she does not drop body condition drastically before we can bring her up to intake levels that fill lactation energy requirements.  Mares should be at about a body condition score 6 when they foal so that they have sufficient energy reserves for early lactation as well as to maintain condition for re-breeding. If she is in a significant negative energy balance (losing body condition) she is much less likely to rebreed easily and carry the next pregnancy.

To bring a mare along properly in her nutritional journey, here are some general guidelines to keep in mind:

  • Good quality pasture or forage may provide sufficient energy thru late gestation, but may not provide adequate amino acids and minerals. 
  • A ration balancer product or a feed designed for pregnant mares may be used from month 5 to about month 10 or 11 of gestation to provide the missing nutrients. 
  • A feed designed for broodmares and foals should be introduced prior to foaling, so that the mare is properly adjusted to the feed well before she foals.  She is under quite a bit of stress immediately before foaling, so this is not the time to be introducing a new feed. This feed can then be increased after foaling to provide both the increased energy and the increased nutrients that are required for lactation, as well as providing nutrition for the foal when it starts to nibble on feed. 
  • Fresh clean water and free choice salt should also be available at all times.
  • The mare should also be vaccinated properly before foaling so that her colostrum, the rich first milk, contains antibodies to protect the foal.  Proper nutrition will also help immune response to vaccinations.

During lactation, a mare’s energy needs are easily doubled over her maintenance needs, and while a mare is producing milk for her offspring, her water consumption can exceed 50-100% that of a maintenance horse. Around 13-24 weeks after the mare has given birth, her milk production will begins to decrease, and the diet can start to be cut back slightly as nutritional needs are getting back to those of a normal maintenance horse.

Feeding the broodmare properly can help reduce the risk of developmental problems for the foal and help insure that the mare can be rebred in a timely manner to produce another foal the following year.

Inside the Broodmare’s Belly…

Lactation demands a lot from a broodmare!

Are you anxiously awaiting that first foal of the spring? Do you have the foaling stall ready, the vet on speed dial, and the video camera on the battery charger? While you’ve been busy prepping, here are some of the amazing changes that have taken place (or are about to take place) in your mare:

  • 6 Month Mark: During 2nd half of pregnancy, 60 – 65% of fetal growth occurs!
    • Energy requirements of the mare go up almost 30% over a normal maintenance horse – from 16.7 Mcal DE per day to 21.4 Mcal DE per day.
    • Her protein requirements will increase 32%, and vitamin and mineral requirements also increase significantly during this time.
    • The mare needs to be receiving adequate calcium, phosphorus, magnesium, copper, zinc, manganese and selenium to provide minerals for the development of the foal and to build the foals own trace mineral reserves.  Trace minerals are also critical for immune support. 
    • Adequate protein/amino acid intake is essential – lysine, methionine and threonine, the first 3 limiting essential amino acids, need to sufficient in the diet for placental and fetal development.
  • Last Trimester: The average foal fetus will grow by 1 pound per day!
  • Lactation: After the foal has been born the real work for the mare is just beginning.
    • The normal mare will produce around 24 lbs (3 gallons) of milk per day. During an average 150 day lactation, this equals 450 gallons or 1.75 tons of milk!
    • During lactation, a mare’s energy needs are easily doubled over her maintenance needs – from 16.7 Mcal DE per day to 31.7 Mcal DE per day!
    • While a mare is producing milk for her offspring, her water consumption can exceed 50-100% that of a maintenance horse.
    • Around 13-24 weeks after the mare has given birth, her milk production will decrease from 3% of her body weight to around 2%.

With all that effort going into producing a darling new foal for your farm, be sure to give your mare an extra pat on the neck, and of course, make sure you are feeding her properly!