The moment you’ve been waiting for has arrived! Your foal has 4 feet on the ground, your mare is letting baby nurse, and your veterinarian has told you both mare and foal are healthy.

Producing high-quality milk for the foal requires a lot from your mare. Lactation puts higher energy demands on a mare’s body than any other stage of her life. [1]

To keep up with the milk requirements of a growing foal while maintaining her body weight, your mare requires a calorie- and protein-rich diet.

During early lactation, energy requirements are 84% higher and protein requirements are 232% higher. Requirements for key minerals such as calcium and phosphorus also increase.

Mares will consume more feed to match increased nutrient demands. They also use body reserves of calories, protein and minerals to support milk production.

Supplying high-quality forages and additional feeds as needed can minimize loss of body condition during lactation and help maximize milk production. Adequate vitamin and mineral supply is also important for maintaining mare and foal health. [2]

Milk Production in Horses

The first milk your mare produces after foaling is called colostrum. Colostrum is rich in antibodies and provides the foal with passive immunity. The antibodies provided in colostrum protect the foal during the first several months of life while the foal’s own immune system is developing.

Within 24 hours of birth, the mare transitions to making milk with a much different composition than colostrum. By three weeks post-partum, the milk composition becomes fairly stable for the remainder of lactation.

Mares can produce in excess of 3% of their bodyweight in milk per day. [1] This high lactation volume continues for approximately 3 months at which time production tapers off as her foal starts to eat solid food. [2]

How Much Milk Does your Mare Produce?

The amount of milk your horse produces can be estimated from her body weight and the day of lactation.

The National Research Council’s Nutrient Requirements of Horses uses the following formula to estimate milk production: [15]

Milk yield (kg / day) = (0.0274287 x BW) x d0.0953 x e-0.0043d

In this equation, d is the day of lactation and BW is body weight in kilograms (kg).

Using this formula, milk production for a 500 kg / 1100 lb horse at one month is estimated at 16.7 kg (L) per day. This will decrease to 10 kg (L) per day by 6 months of lactation.

For the first 3 months, your mare will produce roughly 3% of her body weight as milk per day. This decreases to 2% of her body weight for the next 3 months.

At 6 months of lactation, the foal is relying less on milk as he or she begins to consume more solid feeds.

Mare Milk Composition

Mare’s milk is lower in protein and fat than cow or human milk. However, it is higher in lactose (milk sugar) than cow’s milk, making it similar to human milk. [16][17][18]

Energy 480 kcal/kg
Fat 1.21%
Protein 2.14 %
Lactose 6.37%
Saturated Fatty Acids 47% of fat
Unsaturated Fatty Acids 53% of fat
Vitamin A 0.403
Vitamin D 4.93 ug/L
Vitamin E 1.13 mg/L
Vitamin K 17.93 ug/L
B-carotene 0.388 mg/L
Calcium 0.05 – 0.135%
Phosphorus 0.02 – 0.121%
Potassium 0.025 – 0.087%
Magnesium 0.003 – 0.012%


These values represent averages of mare’s milk taken across several studies. An individual mare’s milk volume and composition can be affected by several factors including: [18]

  • Breed
  • Season
  • Stage of lactation
  • Age of mare and number of previous lactations
  • Mare’s diet
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