Nutritional Needs for Mares in Late Gestation

Breeders with mares in late gestation need to remember that the mothers-to-be have different nutritional needs than open (nonpregnant) mares.

"A pregnant mare's nutrient requirements are slightly higher because she is maintaining not only her bodily needs but also is supplying nutrients to a growing fetus," said Dave Freeman, PhD, Oklahoma State University Cooperative Extension equine specialist.

In the last 90 days of pregnancy, fetal growth increases the mare's energy requirements. Since grain mixes typically have more digestible energy per pound than pastures or grass hay, Freeman suggests increasing the amount of grain fed per day.

"This increased energy demand is met usually by simply increasing the daily allotment of grain by a few pounds per day for mares weighing in the 1,000 to 1,200-pound range," Freeman said. He added that, "It's important for a mare to remain in fleshy condition if she is to be rebred following foaling."

Additionally, Freeman said, added stress brought on by early lactation can cause a mare in marginal body condition to drop to the point of negatively affecting rebreeding efficiency.

Pastures are at their lowest nutritive value during winter, when many mares are approaching parturition. Closely monitor the body condition ofmares turned out on pasture so that grain and hay levels can be adjusted accordingly.

Protein requirements for the mare in late gestation also are slightly higher than for an open animal. Daily crude protein requirements increase about a third of a pound in late gestation. Freeman said that the "increased need usually is met when the mare is fed more grain mix to supply adequate energy, so a higher percent protein ration generally is not necessary."

Calcium and phosphorus requirements also increase during late gestation. A mare requires approximately 10 grams more calcium and phosphorus when approaching her foaling date. As with protein, these amounts typically are met when increasing the amount of grain mix for energy purposes.

"The major vitamin concern during late gestation is vitamin A," Freeman said. "Vitamin A requirements can double in late gestation and lactation." Most commercially prepared grain mixes have sufficient levels of added vitamin A to meet the mare's increased requirements adequately. Still, some broodmare managers feed a vitamin premix to guard against questionable vitamin levels.

"Vitamin requirements are such that supplements should contain a minimum of six-to-one vitamin A to D and be fed at levels recommended on the label," Freeman said.

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