Mares in late gestation (nine to eleven months) experience increased nutritional needs. Consistently meeting a broodmare’s energy and nutrition needs positively influences their reproductive abilities long term.

Adequate intake of nutrients is important according to David Freeman, PhD, extension equine specialist with Oklahoma State University Cooperative Extension Service, who said, “Grain mixes have more digestible energy per pound and have supplemental protein, minerals and vitamins to ensure sufficient intake.”
According to Dawna Voelkl, DVM, assistant teaching professor and specialist in theriogenology at the University of Missouri College of Veterinary Medicine, “approximately 40 percent of fetal growth occurs in the last three months of gestation. And, the final 25-30 percent of fetal body weight is gained in the final month of gestation.”

“Since each mare is different, energy needs will also be different and require variable feeding combinations of pasture grass, grain fed mixes and grass hay, being careful not to feed endophyte-infected fescue,” Russell said.

Although vitamins A, D and E are all major concerns, Freeman said, “Vitamin A is the largest, followed by Vitamins D and E.”
Voelkl suggested that late pregnant mares be assured 20 mg/day vitamin A. “Since the vitamin content of pasture grass generally decreases when dried into hay, mares without access to pasture should receive supplementation,” she said.

When it comes to crude protein, Voelkl said requirements increase by at least 20 percent in late gestation. Freeman said such requirements are best met by supplementing grain to pasture, or feeding higher protein forage to supplement a native grass pasture.

Calcium and phosphorus requirements also increase during late gestation. “Late gestation mares should be supplemented with up to 0.095 g Ca/kg body weight/day,” Voelkl said.
Because excess amounts of phosphorous relative to calcium interferes with calcium absorption, Voelkl recommended the ratio of calcium to phosphorous should be no less than 1:1, but may reach 6:1.

To ensure adequate amounts of sodium, potassium, magnesium, cobalt, iodine, copper, zinc and manganese, Voelkl suggested ad lib access to a commercially available vitamin and mineral block designed specifically for horses.

Unrestricted access to water should be available. “Late gestation mares maintained at approximately 70°F drink up to 50 liters (12-13 gallons) of water per day,” Voelkl said.
To birth healthy foals year after year, broodmares must have nutritional needs met for all stages of production but especially during late gestation.


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