Nutrition For The Pregnant And Lactating Broodmare By Dr. Kiser Of Badger Equine Veterinary Services

A healthy foal starts with a healthy broodmare.  The economic success of a broodmare hinges on her ability to foal early in the year, be rebred and conceive quickly, and to nurse a healthy, growing foal that develops normally.  While there are many factors that contribute to a broodmare’s success, nutrition is one important component in an effective breeding operation.

Proper nutrition prior to and throughout pregnancy is very important, but is most critical during the first and last trimesters.  During the first seven months of gestation, the foal develops slowly – approximately 0.2 lb per day.  However, the first trimester is a critical time for the fetus and proper nutrition is necessary for optimal fertility in the mare.  Underfeeding may cause embryonic loss during the first 36 days of gestation. During late gestation, her dietary needs change significantly.  At this point, the fetus is growing rapidly and increasing in weight by 1 lb per day.  This accounts for approximately 2/3 of total fetal growth.  Amino acids are necessary for tissue development, while vitamins and minerals are needed for proper cartilage and bone development.


Broodmares should be kept in good condition year-round, but especially as the breeding season draws near.  While we usually like to see most horses at a Body Condition Score (BCS) of 5/9, a broodmare should be slightly more fleshy, with an optimum BCS of 6/9.  In comparison to mares at a BCS of less than 5/9, mares at greater than 5/9 are expected to cycle earlier in the year, have fewer cycles per conception (less breedings to obtain a pregnancy), have a higher pregnancy rate, and maintain the pregnancy easier than thin mares.  Wet mares at a BCS of 5 or less do not have enough fat stores to support efficient reproductive performance.  These mares are using their dietary nutrition moreso for milk production rather than reproduction, and are more likely to skip a breeding season.  As previously mentioned, underfed mares are more likely to lose an early embryo.

Overnutrition in broodmares is also a common problem.  We want to take good care of these horses, so they are overfed and become fat, with body condition scores over the recommended 6/9.  While a BCS might affect a mare’s reproductive ability, a BCS greater than 6 can harm fetal development, impact placental function, and effect nutrient transfer to the developing fetus.  There have been metabolism differences between foals born to mares at the appropriate body condition versus mares that are overconditioned, specifically in their glucose and insulin levels.  Research at Texas A&M University found that as a mare’s glucose and insulin increased with more concentrate feed supplementation, is altered the glucose tolerance in both the mare and foal.  If a mare is fed a high-starch diet, it promotes higher levels of insulin in the mare, which may lead to unfavorable metabolic programming in the foal.  Obese broodmares may lead to reduced glucose tolerance, altered pancreatic function, reduced insulin sensitivity, and modified body composition in the foal, which can cause metabolic issues in the foal’s future.  Overly fat mares also tend to have a higher incidence of foaling problems than thinner mares, and a reduction of milk production due to fat accumulation in the udder.


During the early part of pregnancy, mares should be fed at a maintenance level of 1 Mcal/per lb of feed.  This generally equates to 15 lb of good quality pasture and forage for the average sized mare (1,100 to 1,200 lb mare), with free-choice access to a trace mineral block.

At about 5 months gestation, the mare may require a daily mineral supplement in the form of a ration balancer pellet in order to meet the increasing mineral requirements of the mare and developing fetus.  This ration balancer should be fed at 1 to 2 lb a day during mid-gestation, and should be introduced and increased slowly over 5 to 7 days.

During late gestation, the mare’s diet should be gradually increased to 15 to 20 lb of good quality hay, plus 6 to 8 lb of concentrate feed, such as a Mare and Foal type grain.  The greatest amount of mineral retention in the unborn foal occurs at 10 months gestation, so access to free-choice mineral block is always a good idea in order for the mare and the foal to receive an adequate supply of these important nutrients.


At foaling, the mare requires more protein, energy, calcium, and phosphorus in order to recover from foaling stress, produce milk, and prepare for rebreeding. Feeding a foal is a huge energy and nutrient drain on the mare.  Generally, mares produce an average of 24 lb (3 gallons) of milk daily during a 5 month lactation period.  These mares require between 2 to 3 percent of her body weight in total feed daily, which may be as much as 25 to 30 lb of hay and 10 to 15 lb of concentrate feed daily (Refer to table 3 below).  Including fat in her ration increases the fat content in the milk, which may help nursing foals to grow.  Fat inclusion also helps to maintain hard keeper mares and mares that are prone to significant weight loss during lactation. Mineral block access is still important at this stage for foal development.  No matter what type of concentrate the mare is being fed, it should be increased slowly over a week to 10 days to avoid digestive or metabolic issues.

In the 4th to 6th month of lactation, the mare’s daily requirements begin to decline.  Although the milk volume does not change much over a 5-month period, the energy content of the milk decreases significantly.  In the fourth month of lactation, a mare’s milk provides less than 30% of the total energy needed by her foal.  At this point, the foal should be on a good creep feed to meet their requirements, and will begin to cut back on the mare’s diet.  By the time the foal is weaned, the mare should be able to be managed as an early gestation or idle horse again.

Proper nutrition of the broodmare through gestation and lactation will help to give her foal the best start in life, and will help to shorten rebreeding time and improve conception rates.  With all the financial and time investment it takes to get a foal, you don’t want to cause any issues due to nutritional imbalances.  If you have any questions regarding the health of your broodmare or foal, feel free to call Badger Equine Veterinary Services for more information and a nutritional plan that is designed for your mare.