As breeding season begins, James Brendemuehl, DVM, PhD, Dipl. ACT, an equine veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana, is often consulted about broodmare health.

Brendemuehl explains that nutrition is key to ensuring a healthy pregnancy. Proper nutritional support of broodmares improves fertility and promotes normal growth and vigor of the developing fetus. During the first eight months of gestation, mares’ energy needs are the same as those for maintenance, but energy requirements gradually increase over the last three months of pregnancy, when up to 65% of fetal growth occurs.

The growing fetus increasingly takes up abdominal space during the last trimester, requiring the feeding of some grain and good quality hay. Mares in late gestation also need increased protein intake: 10-12% percent crude protein in the last three months compared with about 8% for maintenance and early pregnancy.

Brendemuehl recommends focusing mineral intake on calcium and phosphorus. Mares should receive calcium at a rate of 0.2% for maintenance and early pregnancy and 0.4% for late gestation. To maintain proper phosphorus:calcium ratios for bone health, phosphorus levels should not exceed calcium levels in late gestation. Because legume hays such as alfalfa are high in both calcium and protein, feeding these in late gestation may eliminate the need for calcium and protein supplementation in the diet