Feeding the broodmare

Feeding the broodmare

Mare owners spend thousands of dollars on stud fees and hundreds of dollars in veterinary care to prepare their mares for breeding and foaling. Over an 11-month gestation, mares are expected to grow a healthy foal and then produce enough milk to nourish that foal for up to six months. Furthermore, many mares are expected to raise healthy foals year after year, requiring successful rebreeding while the previous year's foal is still by her side. Because nutrition influences each stage of the broodmare's production cycle, nutritional management may, in many ways, determine the success of the breeding program. 

Broodmare nutrition can be broken down into several different stages: conception, early, mid and late gestation, and lactation. Nutritional management is a simple, yet cost-effective tool that we can apply to ensure normal reproductive cycles, improved conception rates and increased pregnancy maintenance in mares to ensure overall reproductive success. 

Step one: Preparing your mare for successful conception

The effect of nutrition and body condition on reproduction in mares has been clearly illustrated. Mares coming into the breeding season in optimal body condition start cycling earlier than mares in poor body condition. Thinner mares also have difficulty conceiving and maintaining pregnancy as compared to mares in optimal body condition. Some obese mares continue to cycle throughout the winter when, typically reproductive cycling is shut down. There are negative repercussions for keeping mares in this condition. Obesity has been associated in horses and ponies with decreased insulin sensitivity, and both obesity and decreased insulin sensitivity have been associated with decreased reproductive function in mares. Obese mares can have a longer interval between ovulations, which can be due to a persistent corpus luteum. This makes the obese mare more difficult to rebreed if an initial breeding is not successful, increasing the cost incurred by the owner.

What is the best BCS for breeding mares?

When preparing a mare for breeding, it's ideal for her to be in slightly above-average condition, aiming for a body condition score (BCS) of 3–3.5 out of 5, or 6–7 out of 9. Preparing your mare for pregnancy is also a great opportunity to review your mare’s diet to ensure all minimum nutritional requirements are being met, as nutrient deficiencies can negatively impact reproductive health. Providing a solid nutritional foundation is one of the most important steps in setting your mare up for a successful pregnancy.

Key nutritional considerations:

Hard feed:

• Is the feed you are providing appropriate for her metabolic needs?
• Are you feeding according to the feed’s guidelines? 
• Does she require a vitamin and mineral supplement to fill any nutritional gaps?
  

Pasture: 

• Is she receiving enough fibre/roughage from pasture alone? If not, does she need additional hay to meet daily roughage requirements?

Pasture type:

• Is she grazing on high-oxalate pasture such as Kikuyu or Buffel grass? If so, it is essential to provide a calcium supplement, as oxalates bind to calcium in the digestive system, which can lead to calcium deficiencies.
• Oxalate pastures can also impact calcium-to-phosphorus ratios, which can cause bone issues in both mare and foal. 

Providing a solid nutritional foundation is one of the most important steps in setting your mare up for a successful pregnancy.

Feeding Examples: Underweight vs Overweight Mares

Overweight mares: A combination of Hygain® Balanced® (500g per day) and exercise is ideal to bring them into optimal shape before breeding.

Underweight mares: Hygain® Tru Breed® (2kg + per day) has high feeding rate requirement and calories to help increase condition in preparation for breeding.

Step two: Nutritional requirements for mares in early and mid-gestation

From conception through foaling, the foal is actively growing, but growth does not occur at a steady rate. During the first seven months of pregnancy, foetal growth is slow, accounting for less than 20% of birth weight (around 2% of the mare’s body weight). Rapid growth occurs in the final trimester.

Because of this, the nutritional requirements of a mare in early and mid gestation are very similar to those of a non-pregnant mare. A common feeding mistake is to overfeed calories during this stage, leading to overweight mares, which can negatively impact reproductive health and foaling outcomes.

What to feed mares in early pregnancy?

An all-forage diet (good quality hay or pasture) generally provides enough calories and protein for most mares in the first half of pregnancy. However, forage alone is often deficient in essential minerals and vitamins.
Feeding a fully fortified feed such as Hygain® Grotorque® or Tru Breed®, alongside quality roughage/forage, helps ensure the mare is meeting her essential nutritional requirements. 

Common feeding mistakes in early and mid gestation: 

Overfeeding energy: Many owners mistakenly feed too many calories too soon, which can cause weight gain and reduce reproductive efficiency.

Ignoring mineral deficiencies: Pasture or hay alone often falls short in calcium, phosphorus, copper, and zinc, which are all vital for mare and foal health.

Not reviewing diets: Nutritional requirements change throughout pregnancy, so a review every few months is recommended.

Maintaining steady body condition and regular diet reviews supports both the mare’s long-term health and the developing foal. A balanced diet in early and mid gestation lays the foundation for healthy foal growth in the final trimester.

Step three: Nutrition for mares in late gestation (last trimester of pregnancy)

During the last trimester of pregnancy, the foal will gain approximately 80% of its birth weight. To support this rapid foetal growth, the mare’s requirements for energy, protein, vitamins, and minerals increase significantly.

Why are trace minerals critical in the last trimester?

Trace minerals are especially critical in late gestation. The mare fortifies the foal’s liver with copper, zinc, and selenium before birth, as mare’s milk is not a good source of these nutrients. The foal relies on these liver stores during the first two months of life to support proper skeletal development and bone strength.

Without adequate trace mineral intake, foals may be predisposed to growth disorders and developmental problems.

Nutrition challenges in the last trimester of pregnancy

Alongside the increased demand for nutrients, mares in late pregnancy have a limited capacity for feed intake. The size of the growing foal compresses onto the digestive system, which may reduce appetite in some mares and may affect hay intake.

Best horse feeds for mares in late pregnancy

The Hygain® Breeding Range is specifically formulated to meet the needs of mares in the final trimester:

Hygain® Grotorque®: A concentrated, highly palatable micronized muesli feed rich in quality protein and bioavailable minerals for improved uptake and absorption. You can feed less Grotorque® to meet nutritional requirements. 

Hygain® Tru Breed®: An extruded feed designed for poor-doing or hard-keeping mares, supplying essential protein, energy, and balanced levels of macro and micronutrients. It also supports pregnant mares, lactating mares, and growing horses for optimum health, fertility, and growth.

Step four: Feeding lactating mares (nutritional requirements after foaling)

The lactating mare has the highest nutrient requirements of any horse on the farm. At peak lactation, the mare produces 8-12L of milk per day (Fišera et al, 2020). To produce milk and to repair the reproductive tract in preparation for future pregnancy, the mare requires substantial amounts of energy, protein, calcium and phosphorus. To maintain both adequate milk production and body condition, lactating mares will often need to be fed substantial amounts of grain and high-quality forage. Without adequate energy (calorie) intake, mares will lose body weight and may have problems conceiving. 

The most common feeding mistake made with lactating mares is to underfeed them and not meet nutritional demand. If a mare does not receive sufficient nutrients during lactation, she will draw upon her own body reserves to maintain the quality of her milk for her foal. Most importantly, she must be provided with a quality source of protein along with adequate calcium and phosphorus. Without this, she will catabolise her own muscle tissue for amino acids and mobilise calcium and phosphorus from her bones. Over time, this can lead to reduced muscle mass, decreased bone density, and an increased risk of long-term health issues (Fišera et al, 2020). 

Protein and amino acid requirements increase substantially from late pregnancy to lactation. More specifically, lysine requirements more than double in lactating mares compared to late pregnancy. Lysine is an essential amino acid that horses cannot synthesise themselves and must be supplied through diet (Geor et al, 2020). Ensuring adequate dietary lysine intake during lactation is crucial for maintaining milk lysine levels and supporting optimal foal growth.

Maintaining optimal conditions is also essential. A foal can also quickly lower the condition in the mare, and lactating mares in thin condition may take longer to rebreed and have lower pregnancy rates than mares in a moderate to fleshy condition.

Feeding recommendations for lactating mares:

Provide lucerne hay:

• For an early lactating mare, lucerne hay is highly recommended to meet calcium, phosphorus, and protein requirements. 
  For a 500 kg aim to provide a minimum of 2–3 kg per day in addition to grass hay or pasture. 

Prevent excessive weight loss:

• Lactation is highly demanding on the mare’s body, and many mares lose condition during this period. To prevent excessive weight loss, increase hard feed intake to meet her megajoule (MJ) energy requirements. For example, for a 500kg horse, you may need to increase her hard feed up to 4kg per day. Tru Breed® and Prodigy®  are great feeds to ensure poor doing lactating mares get the nutrients and calories they need to maintain weight. 
• Consider adding oil to the diet to increase fat intake without significantly increasing feed volume. For example, a 500kg horse can have up to 250mls of oil per day. 

For good doers/easy keepers: 

• If your mare cannot receive increased feed without risking excessive weight gain, consider providing a high-protein, amino acid-concentrated feed such as Balanced®.
• Balanced® contains 250 g of protein and 20 g of lysine per kilogram, helping to meet essential nutrient requirements in smaller quantities.
  

References:

Fišera, M., Kráčmar, S., Šustová, K., Tvrzník, P., Velichová, H., Fišerová, L. & Kubáň, V. (2020) ‘Effects of the lactation period, breed and feed on amino acids profile of mare’s milk’, Potravinarstvo Slovak Journal of Food Sciences, 14, pp. 562–572. doi:10.5219/1344.

Geor, R. J., Harris, P. A. & Coenen, M. (2013) Equine Applied and Clinical Nutrition[HM1] [ET2] : Health, Welfare and Performance. 1st ed. Saunders (Elsevier Health Sciences). Print ISBN: 9780702034220.