Where #SeriousHorsePeople come to better understand digestive health in horses and its impact and management.

Study Shows Feed Broodmares Forage Continuously for Increased Fertility


It’s no secret that healthy, successful pregnancies start with healthy mares, so chances are, you already have a good routine in place for keeping your mare in top shape leading up to the breeding season.

While it goes without saying that your mare will need a safe, warm place to foal, you also need to pay special attention to her health and nutrition. It’s important to have a feeding strategy in place to help your mare get additional calories, protein, calcium and phosphorous, and a plan to keep close tabs on her weight, as pregnant mares should rank slightly higher on the Henneke Body Condition Scale than other mares (although not too high, as obesity can lead to a host of health issues).

Because of these increased needs, many horse owners turn to expensive, specially formulated feeds for their broodmares. In moderation, feeding a small amount of these feeds can be beneficial for some mares. But more often, the kinds of high-fat, starch-ridden sweet feeds that are marketed to the owners of broodmares may cause more harm than good by creating:

As we wrote in this Monday Myth, using grain to prepare your mare for the breeding season is generally a mistake because it interferes with her digestive system. We advocate constantly for a forage-first approach to feeding all horses for better digestive health — but recent research also suggests that prioritizing free access to forage may also make your mare more fertile.

The Connection Between Continuous Foraging and Improved Fertility in Mares

According to a 2013 peer-reviewed study published in PloS One, mares that had continuous access to hay or grass around the clock:

  • Were much more likely to be in foal by mid-June than horses with restricted access to forage.
  • Were nearly twice as likely to conceive on the first insemination, as compared to the mares with less grazing time
  • Had more regular cycles.

The study, beginning April 1 and concluding June 11, examined 100 Arabian mares in good general and reproductive health. All broodmares were fed the same type and amount of feed, managed in the same environment and in the same way. The sole difference was that one group was only given hay at night while the other’s portion was distributed throughout the day and night so the mares could eat nearly continuously. Those mares foraged an additional six hours per day from 9am to 3pm, a time when horses in natural conditions tend to feed most.

Data was then collected regularly from all mares. Estrous was detected every 48 hours, mating or insemination performed every 48 hours until ovulation was detected, and ultrasounds performed 15 days after ovulation to confirm pregnancy.

While the correlation between continuous feeding and reproductive success was clear, the reasons why require additional examination. Ongoing research suggests that:

  • Restricted feeding time stresses horses mentally and physically, and stress is known to have a negative impact on reproduction.
  • Continuous forage improves metabolism in horses, triggers digestion, and encourages a healthy gut, so the mares may have an enhanced body condition better for reproductive success.

According to the study, allowing a mare to have frequent or constant access to forage may make her healthier more comfortable and calmer. Translation: a happier mare = a more fertile mare.

Are you a veterinarian or breeding manager? Read our more in-depth review of this study here.

Feed Forage Continuously for a Healthier Broodmare

If your climate and barn situation allows, turn your mare out as often as possible. Just be aware that you may need to supplement with regular amounts of high-quality hay, as the pasture grass won’t maintain a high enough nutrient content. If you live in a colder climate, you’ll need to prioritize hay and other sources of forage fed free-choice or broken into many smaller meals throughout the day.

Researchers in the PloS One study found that conception rates were 47% higher in mares allowed to feed continuously over 23 hours, compared to those that had access to the same amount of forage, but for only 17 hours a day.

In other words: feed forage constantly!

Take Steps to Support Digestive Health in Your Broodmare

The results from this study on fertility and forage suggest a direct link between digestive wellness and fertility. Using that logic, it makes sense that anything you can do to support your mare’s digestive system is a benefit.

Since growing a foal is hard work, it’s important to do as much as we can to help keep broodmares healthy during the process through good feeding and management practices and taking specific steps to support digestive health.

Photo by Hunter Desportes, licensed via CC2.0.

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