Nutrients in Mare’s Milk and Their Foals’ Skeletal Development

In most cases, mare’s milk will provide 100% of the nursing foal’s nutrient requirements. But what happens when her milk is not adequate to meet the foal’s nutritional needs? A shortage of major and/or trace minerals in the milk of a suckling foal can cause nutritionally induced Developmental Orthopedic Disease (DOD). This can appear in several different forms in growing horses and is described as a disturbance in the formation of cartilage or in the conversion of cartilage into functional mature bone. These can include:

  • Physitis
  • Bone cysts
  • Contracted and acquired contracted flexor tendons
  • Angular limb deformities (valgus or varus)
  • Osteochondrosis (OC)
  • Osteochondritis Dissecans (OCD)
  • Abnormalities in the formation of the neck vertebrae, causing wobblers

The nutrients found in mare’s milk can be affected by:

  • Genetics of the mare
  • Nutrition of the pregnant and nursing mare resulting from:
    • An unbalanced or inadequate diet, causing nutrients to be below optimal levels (“2007 NRC for Horses,” pages 311-314)
    • A diet fed below the mare’s needs for protein (amino acids), decreasing the quality and quantity of her milk
  • Health of the mare
  • Stresses can affect the mare’s health, lowering her ability to provide quality and quantity milk to her foal

If any of these DOD problems occur in a foal before they begin consuming an adequate amount of a fortified dry feed, we will look into the possibility of low mineral density in the mare's milk as a potential cause. Published research has stated trace mineral supplementation is beneficial in the sucklings’ diet when the mare has previously produced a foal with DOD. Comparing your mare’s actual milk analysis to the NRC’s for Horses average milk analysis may shed some light on the cause of the problem. Once we know the level of nutrients in the mare’s milk, we can develop a supplementation program for the foal to make up for these shortages, if necessary.

Completing an Analysis of Mare's Milk

To take advantage of this information, the first step is to get the milk analyzed. Collect at least 3 oz of milk from your mare (download proper collection instructions here) and pour into a clean plastic bottle with a tight screw cap. Label it with the name of your mare, your name, address, and phone number, and then send it overnight along with a completed copy of the Mare's Milk Analysis Information Form to:

Holmes Laboratory, Inc.
3559 U.S. 62
Millersburg, Ohio 44654
Phone: 330-893-2933 or 800-344-1101
Email: [email protected]

Provide them with your email address on the Information Form and the lab will send you the results on the third working day after they receive the sample. Request “Test B” and include a check or money order for $42/sample. If nutrient shortages are found, the Progressive Nutrition® staff will review your milk analysis and formulate a comprehensive plan to make up for the deficiencies in the milk.