A mare during pregnancy does need
extra nutritional support leading up to foaling.

However, during pregnancy, the alterations to her diet are not extreme. She only requires gradual increases to meet her nutritional needs over the last few months of gestation. However, once a mare foals, her nutritional demands increase dramatically - so much that her dietary requirements post-foaling have been compared to that of a racehorse under intense training.

Mares are obviously physically challenged after foaling. Once the mare has given birth, she shifts from supporting the gestating foal to lactation in support of her newborn foal. Thus, it is vital that horse owners are aware of a mare’s changes to her nutritional needs. These can be reviewed in our Feeding the Lactating Broodmare article.

Another major consideration for the mare is her recovery from a long 11-month pregnancy. Since the goal of most broodmare operations is for their mares to carry a foal each and every year, their reproductive tracts must recover quickly enough to conceive another pregnancy. Within a few days after giving birth, mares enter what is called a “foal heat.” This is a fertile reproductive cycle where the mare can be bred and get pregnant. It is the goal of most broodmare operations to get a mare pregnant during this foal heat cycle. This ensures the mare can carry and produce a foal year after year.

Obviously, the weeks following foaling will be a nutritionally challenging time for any mare. It is also a challenge to get her pregnant quickly. As we discussed in our Nutritionally Supporting Your Broodmare and Foal article, a key component in helping your mare through this transitional period is to keep her in an above average body condition score (BCS). The generally recommended BCS for a broodmare is around 6.5. Research has demonstrated that fleshy (BCS 6-7) broodmares:

  • Have fewer cycles to conception and higher conception rates during foal heat.
  • Have higher overall pregnancy rates.
  • Will cycle earlier in the year.
  • Will maintain their pregnancies at a higher rate compared to thinner (< BCS 5) mares.

Anything above a BCS of 7.5 is not recommended, as reproductive studies have shown that obese mares have difficulty conceiving and even have difficulty carrying their pregnancies. At the other end of the spectrum, studies have shown mares with anything less than a BCS of 5 produce less milk for their growing foals and also have difficulty conceiving.

Immediately after foaling, the mare’s uterus goes through a process called “involution.” This is a period where the mare’s stretched reproductive tract goes from carrying and supporting a ~100 lb. foal at birth to contracting back to its original size. In horses, this process usually happens quite quickly. Within 30 days of foaling, her uterus should mostly be recovered. However, during this process, her reproductive tract is under tremendous stress.

While most nutritional studies in postpartum mares have focused on supporting her during lactation, few have focused on the direct affect her diet has on her reproductive status. Of the studies conducted, many have looked at inflammation and oxidative stress in the mare post-foaling. They have shown there is a correlation with delayed involution in postpartum mares and higher markers of inflammation. This has led to delayed involution and a risk of the owner not being able to breed the mare that year. Thus, a diet higher in antioxidants is beneficial. Additionally, some studies have shown that added amino acid support, such as L-arginine and L-glutamine, can be beneficial to postpartum mares and improve their involution and pregnancy rates. Other studies have even evaluated vitamins and minerals and their influence on a postpartum mare’s reproductive status. Overall, the studies are in general agreement that with proper nutritional support, owners can increase their chances of that mare conceiving quickly after foaling.

So, how can you best support your postpartum mare during these critical few weeks following foaling? First, a general feed designed for non-lactating or non-breeding animals will not be sufficient to support a lactating mare. In fact, it may also hinder her ability to be rebred quickly. Thus, here are some helpful nutritional feeding guidelines for the post-foaling broodmare:

  • Feed high quality forage. Lower quality forage will be devoid of critical nutrients.
  • Supplement the mare’s diet with a quality feed fortified with amino acids, vitamins, minerals and other nutrients.
  • Ensure free-choice access to clean water. The water intake of lactating mares nearly doubles.
  • Expect some drop in body condition during peak lactation. However, with high quality feeds and forages, mares will gain condition throughout their pregnancies in preparation of foaling the following year.
  • Always be sure to transition your mare’s diet slowly.

Broodmares, especially leading up to and following foaling, require careful management. However, with a proper feeding plan, and with careful adjustments to her diet, broodmares and their foals thrive. If you have any questions or concerns about what you are feeding your broodmare, please reach out to us directly so we can assist in developing and personalizing a feeding plan for your mare and foal.

Chris J. Mortensen, Ph.D.