Nutritional Considerations for the Broodmare

Broodmare nutrition is an important topic as nutritional requirements change throughout gestation and lactation. Most mares are bred in the spring here in Ontario; however, it is recommended that a mare is on a balanced diet to support her in achieving an optimal body condition prior to breeding.

When I receive inquiries in the spring that are to create a plan for a broodmare to alter their weight by a substantial amount there is a limited range of what I can achieve in such a brief timeline. Therefore, I was motivated to remind broodmare owners to start thinking about the nutritional preparation that their mare may need this fall. I have already had a few bookings for broodmares that are going to be bred this upcoming spring – this is the perfect situation for the Personal Nutritionist Package!

When you have a mare that you are planning to breed, the first consideration starts with nutritional strategies to enhance the likelihood of the mare becoming pregnant. Of course, nutritional management is crucial, but housing conditions, deworming, and regular veterinary care (e.g., vaccinations) are all extremely important factors in broodmare health.

Preparing for Breeding

When we evaluate the research on broodmares, body condition is a critical variable that impacts reproductive efficiency. When a mare’s body condition is below a 5 (on the Henneke 9-point system), they have lower conception rates than mares with a condition of 5 or higher. That being said, when a mare has a body condition above a 7 there are also serious concerns.

What does the nutrition look like in this pre-breeding period?

A balanced diet is crucial, but it doesn’t have to be complicated. Many broodmares will thrive on free-choice quality forage (please test your hay!!!) with a ration balancer. Of course, quality forage can mean different things to different people, so a more precise way to say this would be for your mare to be maintained on a forage that has been tested and is adequate for meeting her basic nutritional requirements. Nutritional deficiencies can be truly detrimental, so having your forage tested and your mare’s diet balanced by a nutritionist is a worthwhile investment.

Now that we have touched on the easy keepers, what about the mares that struggle to maintain weight? Unlimited forage with a ration balancer simply isn’t enough for some horses, and to elicit weight gain a concentrate often needs to be added. There are two broad categories for concentrates; you have straight cereal grains and commercial concentrates. Both of these options work, however, I recommend the commercial concentrates as if you are purchasing from a reputable company a qualified equine nutritionist will have been involved in the formulation of that product.

The amount of concentrate that needs to be added will depend on the mare’s current body condition, the timeline to meet her optimal body condition score and of course the caloric content of the commercial product being used. One nutritional issue I commonly see is that people will have a horse that needs some additional concentrate but will feed below the manufacturer’s recommended amount. This typically equates to vitamin and mineral deficiencies – therefore, in these situations, a ration balancer may also need to be incorporated or the commercial concentrate product may need to be exchanged for another. A nutritionist will be able to do all of these calculations for you.

If your mare is under-conditioned heading into the winter months it can be quite difficult to have significant weight gain, therefore, I recommend consulting with a nutritionist in the fall so that they are on the right track, and you have time on your side. Remember, all diet changes need to be made slowly and weight change is a process.

So, now that you have your horse on a balanced diet that is supporting them in maintaining a healthy body condition, what dietary adjustments are required during pregnancy?

Early Pregnancy

During gestation, adequate nutrition not only needs to be provided to the mare so that she can support herself, but she also must support fetal growth during this period. This is achieved either through processing additional nutrients in her diet or by relying on and pulling nutrients from her own body’s stores to meet the needs of the developing fetus.

When I am designing a broodmare diet, the goal is to minimize the need for the mare to use her own body stores. Therefore, as the mare’s nutritional requirements increase during gestation, her balanced diet should also change to meet these increasing needs. The NRC 2007 Nutrient Requirements of Horses states that the pregnant mare starts to require additional nutrition in the 5th month of gestation. As the mare approaches the 5th month, her diet will need to be altered to ensure it is meeting her nutritional requirements as they continue to increase into late pregnancy and lactation.

Late Pregnancy

Starting in month 5 of pregnancy the energy and protein requirements both begin to increase. These will continue to increase through the remaining gestational period. In month 7 is when we begin to see increased requirements for minerals such as calcium, phosphorus, and magnesium.  

The most significant nutritional changes occur in the third trimester as that is when the majority of fetal growth occurs. Additionally, a mare’s appetite may decline towards the end of gestation. This needs to be carefully monitored so that the diet can be altered to meet her increased needs, and if appetite is decreased an increase in concentrate is typically warranted.

For broodmares during pregnancy, it is not concerning if they are slightly over a body condition of 5 /9 as having some additional body fat can help to support milk production after the foal is born. However, this should be monitored carefully as a broodmare being obese can be detrimental to their well-being as well. When a broodmare is obese it is linked to larger foals and a higher incidence of delivery complications.


The highest nutritional requirement for broodmares occurs at the beginning of lactation. The first two months of lactation require significant nutritional support with a slow decrease in nutritional requirements throughout the remaining months of lactation. Also, remember that water is an essential nutrient. During the lactation period a mare will almost triple her water consumption. Therefore, large quantities of fresh water should always be available to your mare.

When considering adding supplemental sources of nutrition above and beyond the forage, such as ration balancers or commercial concentrates, one consideration that is commonly overlooked is the quality of ingredients. Many horse owners will go to the feed store and may look at the feed tag for crude protein percent but may not closely look at the ingredients. However, when designing optimal diets for broodmares, ensuring you are choosing commercial products that incorporate high-quality protein sources and bio available mineral sources can make or break the nutrition program.


Post-weaning isn’t a period that normally gets a lot of attention; however, it is also a critical period nutritionally. Despite a great nutrition program, there is research to show that the mare will still mobilize some body stores, particularly from their bone mineral (e.g., calcium) during lactation. Therefore, when we look at post-weaning, it presents an opportunity for your mare to replenish those stores.

It is not uncommon that a broodmare will be on additional supplemental feed during pregnancy and lactation, but then revert to a hay-only diet after weaning. Part of the reason this is often done is to prevent excess weight gain and reduce the likelihood of mastitis developing as there is research to suggest that reducing feed intake is a recommended practice for the prevention of mastitis. However, a ration balancer should still always be used, even for those easy keepers as your mare should always have a source of additional vitamins and minerals. Relying on a mineral block is not adequate.

To conclude, a balanced diet is crucial through every step of pregnancy for the broodmare, nutritional deficiencies can easily go undetected but can cause lasting health issues in the foal when born. Obesity in the broodmare can cause increased fetal adiposity which can affect growth and performance as well. Due to the continually changing nutritional requirements, I highly recommend working with a nutritionist who can do all the nitty gritty calculations for you in these situations to ensure you are setting both your mare and foal up for success!

If you have any questions don’t hesitate to reach out.

By: Madeline Boast, MSc. Equine Nutrition


Canisso, I. F., Podico, G., & Ellerbrock, R. E. (2021). Diagnosis and treatment of mastitis in mares. Equine Veterinary Education33(6), 320-326.

Henneke, D. R., Potter, G. D., Kreider, J. L., & Yeates, B. F. (1983). Relationship between condition score, physical measurements and body fat percentage in mares. Equine veterinary journal15(4), 371-372.

Morley, S. A., & Murray, J. A. (2014). Effects of body condition score on the reproductive physiology of the broodmare: a review. Journal of Equine Veterinary Science34(7), 842-853.

National Research Council. Nutrient Requirements of Horses. (2007). National Academy Press, Washington, D.C.

Peugnet, P., Robles, M., Wimel, L., Tarrade, A., & Chavatte-Palmer, P. (2016). Management of the pregnant mare and long-term consequences on the offspring. Theriogenology86(1), 99-109.

Robles, M., Hammer, C., Staniar, B., & Chavatte-Palmer, P. (2021). Nutrition of broodmares. Veterinary Clinics: Equine Practice37(1), 177-205.

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