STILLWATER, Okla. — Horse breeders with mares in late gestation need to remember that the mothers-to-be have different nutritional needs than open 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, Oklahoma State University Cooperative Extension equine specialist.
In the last 90 days of pregnancy, fetal growth will increase the mare’s need for energy. Since grain mixes typically have more digestible energy per pound than pastures or grass hay, this means 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 pound to 1,200 pound range,” Freeman said.
Added additional stress brought on by early lactation can cause a mare in marginal body condition to drop to the point of negative rebreeding efficiency.
In addition, pastures are in their lowest nutritive value this time of the year, so close inspection of mare condition is necessary so that grain and hay levels can be adjusted accordingly.
Protein requirements for the gestating mare also are slightly higher than for an open animal. Daily crude protein requirements increase about a third of a pound when mares are in late gestation.
“This 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,” Freeman said.
Calcium and phosphorus requirements also increase during late gestation. A mare requires approximately 10 grams more calcium and phosphorus than when in an open state. 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 as 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.