Diet's Effect on Broodmare Lactation Described (AAEP 2012)

The mare's continued health dictates her milk production and foal growth.

Your foal has finally arrived, and he and mom appear healthy and happy. But don't let your guard down just yet: The mare's continued health dictates her milk production and whether the foal will not only grow but also thrive during his first few months. Supporting her overall and nutritional health becomes especially crucial.

"Lactation places immense demands on the mare, both nutritional and physiological," said Peter R. Morresey, BVSc, MACVSc, Dipl. ACT, ACVIM, of Rood & Riddle Equine Hospital, in Lexington, Ky. He described how to assess and address these needs in a presentation at the 2012 American Associations of Equine Practitioners convention, held Dec. 1-5 in Anaheim, Calif.

He explained that a mare's unwitting goal is for the foal to achieve 45% of his mature weight by the time of weaning. "A number of management decisions and medical conditions can lead to decreased or even lack of milk production that will fail to meet the needs of the growing foal," Morresey explained.

Some of those factors include:

  • Fescue toxicosis;
  • Disease (of the mare or foal);
  • Malnutrition; and
  • Infection (mastitis) or disease (e.g., cancer) of the mammary gland.

"The key to successfully manage lactation issues is to promptly detect and treat failure to lactate," advised Morresey.

For example, in cases of fescue toxicity, avoid allowing the mare to further graze affected pastures. In mares treated with pergolide to manage Cushing's disease, it is advisable in some cases to withdraw the drug 30 days prior to foaling because the drug can cause lactation failure. But aside from fescue and pergolide considerations, one of the most important ways to ensure your mare is producing enough milk is simply guaranteeing she is receiving adequate nutrition.

Morressey reminded the veterinarians that lactation requires a considerable energy. Owners can calculate a pregnant mare's feed requirements (daily energy, fat, protein, etc.) using the formulas detailed in Morresey's abstract. Although they might initially appear complicated, he said the calculations are fairly straightforward. (Editor's Note: The abstract will be available online at in early 2013.)

In addition to recommending ration size, he said to pay attention to feed quality. This could be particularly important considering that late-term pregnant mares' voluntary food intake is generally 20% less than that of nonpregnant mares, due to the increase in fetal size.

Morresey concluded, "Successful lactation depends on normal hormonal activity and a lack of any inhibitory influences on the mare, such as underlying disease, pathology (damage/disease) to the mammary gland, malnutrition, and factors affecting the foal that can reduce normal suckling activity."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.