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High-Quality Milk Essential for FoalsBy Kentucky Equine Research Staff · March 22, 2017

Lactating mares provide the sole source of nutrition for newborn foals. As foals mature, they  begin to sample forage and even grain concentrates, and rely less on the dam’s milk. Providing nutrition to foals requires significant nutrient consumption. How do mares do it?

Lactating mares produce approximately 2-4% of their body weight in milk each day. That means that a 1,200-lb (545-kg) mare will produce 24-48 lb (11-22 kg) of milk per day, equivalent to 3-6 gallons (11-22 liters). Her nutrient requirements are notably influenced by the amount of milk produced. While an average horse requires about 10 gallons of water per day, it is easy to see why a lactating mare requires 50-70% more water to support milk production.

Peak milk production occurs during the first month of lactation, with only a slight decrease during the second month. In fact, milk production only decreases in volume slightly, to a low of about 2% of the mare’s body weight, over 5 or 6 months of lactation. The energy and nutritional value of milk declines more dramatically, however, as lactation progresses.

By the fourth month of lactation, milk provides less than 30% of the foal’s energy needs. The foal has begun to consume creep feed and some forage by this time, gaining nutrition from these sources. When the foal is weaned, usually at 5 or 6 months of age, the mare will slowly stop milk production. The lack of stimulation of suckling and absence of the foal will cause the cessation of milk production and regression of the udder.

According to Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER), “One of the major factors affecting a mare’s milk production is her nutritional status and body condition. Obese mares, with a body condition score (BCS) of 8 to 9, and thin mares, with a BCS of 4 or less, tend to produce less milk compared to mares with a more moderate condition of 5 to 7.”

If a mare’s nutrient intake is above or below what her needs are, it doesn’t have much effect on the volume of milk production. If nutrient intake is less than what is needed, a mare’s body will draw on her own energy reserves to ensure that milk composition is sufficient for the foal. Over time, she may become deficient unless her nutrient intake is corrected and balanced. However, volume of milk is not typically altered based on varying intake of most nutrients.

The most important thing to understand when feeding lactating mares is that their needs will change not only throughout their pregnancy but throughout the lactation period as well. In the first month or two of lactation, a mare’s needs increase, on average, to 50% or more above her maintenance needs, especially for energy, protein, calcium, and phosphorus. This is usually equivalent to between 2-3% of her body weight in feed per day. These needs slowly decline until weaning.

Catherine Whitehouse, M.S., a nutrition consultant with KER, recommends a forage-based diet with the addition of concentrates as needed. “Select high-quality forage and, if necessary, a concentrate feed specifically designed for broodmares and growing foals. Low-quality, all-purpose feeds will not contain all of the nutrients mares and foals require, so it’s prudent to choose feeds appropriate for breeding horses.”

Monitor the mare’s body condition to ensure she doesn’t lose or gain too much weight. Aim to keep her in moderate body condition. As always, any increases in feed volume should be done slowly to minimize risk of digestive upset.

A KER nutrition advisor can help you ensure a mare’s diet is balance to support her own needs along with that of her foal. Start a consultation now.