At foaling, a mare’s daily nutrient requirements increase significantly. The protein and energy requirements almost double from early gestation to lactation, as do requirements for calcium, phosphorus and Vitamin A. These nutrient needs must be met in order for the mare to recover from foaling stress, produce milk and to rebreed, all without losing body condition. This is a critical, nutritional period for the mare. Underfeeding of mares during early lactation will surely lower milk production and cause weight loss. This may not pose a problem if the mare is in fleshy to fat condition. However, early lactation weight loss in mares that foal in thin condition will often affect the mare’s ability to raise her new foal and become pregnant again.
Mares produce an average of 24 pounds (3 gallons) of milk daily during a 5-month lactation. This represents 450 gallons or 1 3/4 tons of milk over 150 days. High producing mares produce as much as 32 pounds (4 gallons) of milk daily. The average production in the first 22 days of lactation is 26.5 pounds per day. Production appears to reach a peak at 30 days and slowly decline from there. Nutrient content of mares’ milk follows a more drastic downward curve. In the fourth month of lactation, a mare’s milk provides less than 30 percent of the total energy needed by her foal. Providing lactating mares with a concentrate that includes added fats or oils and high quality protein can help slow the downward curve of production and improve nutrient content of the milk. This will translate into an early growth advantage for the nursing foal.
A lactating mare will usually consume between 2 and 3 percent of her body weight in total feed (hay + concentrate) daily. Because of the significant difference in nutrient requirements from gestation to lactating, it would be safer for a gradual increase in feed intake to begin prior to foaling. This would prevent a drastic change at foaling time, which could increase the risk of digestive disorders. Also, providing the total daily feed in two equal feedings allows mares to more safely consume the amounts needed during lactation. Heavy milkers may require as much as 1.75 percent of body weight in concentrate feed each day, depending on the quality and nutrient density of that concentrate.
When possible, mares fed in groups should be sorted according to feed intake or body condition to insure each mare receives the appropriate amount of concentrate to meet her needs. Providing individual feed troughs for each mare plus one extra trough for mares that get run off from their feed, or providing plenty of space at group troughs will help insure that mares consume the feed they need.
Free choice spring grazing will meet some of the mare’s nutrient requirements, but considerable amounts of supplemental concentrate will be needed. Less supplemental feed will be needed for mares grazing on small grain pastures. In most cases, body condition of mares on high quality pasture or hay can be maintained with concentrate provided at .75 to 1.25 percent of body weight daily. This will vary significantly depending on the quality and quantity of forage available and the nutrient content of the concentrate.
In the fourth, fifth and sixth months of lactation, daily requirements begin to decline. However, by this time many horsemen will have had foals on a good creep feed to prepare them for weaning and will be weaning by the fourth or fifth month of age. There is no advantage for the foal to remain on the mare past this time. It is more nutritionally accurate for the foal and more economical for the horseman to feed the foal a quality diet to meet his needs directly than it is to feed the mare to produce milk. Once the foal is weaned, the dry, pregnant mare can be managed as an early gestating mare once again. Through proper health care, feeding management and breeding techniques, the mare can produce a strong, healthy foal each year.
By Karen E. Davison, Ph.D., Managing Equine Nutritionist, Purina Mills, LLC