Breeding a mare can represent a large economic and even emotional investment. Once the mare is pregnant our goal is to provide the best care for her so that eleven months later, she can deliver a healthy foal.
A pregnant mare is considered normal when there is no medical reason to think that she is prone to complications during pregnancy or delivery. If a mare is reasonably young, that is less than 20 year of age, and healthy, or there is no history of problems in previous gestations, this is a pretty good assumption. Therefore, with few exceptions, a pregnant mare should be managed and treated as any other horse in the farm:
A pregnant mare SHOULD NOT:
It is important that the mare is in good body condition prior to breeding. Body condition condition is usually scored in a scale from one (most thin) to nine (most overconditioned), and should also be monitored throughout pregnancy. Ideally, mares should go into a breeding program with a body condition score of five. A rule of thumb is that the ribs cannot be seen while the mare is breathing but they can be felt easily when the hand is run smoothly over the rib cage, which means that there is no excessive fat covering the spaces between the ribs. The general body conformation should also be taken into account when evaluating body condition.
Good quality roughage (grass or legume hay) should be the main nutritional source for any horse. In general, horses consume around 1.5 to 2 percent of their body weight in feed or dry matter. Roughage that includes hay and pasture should comprise at least 1 to 1.5 percent of this intake. The remainder may be supplemented with grain depending on the body condition of the horse and metabolic demands.
As pregnancy advances the mare will have increased metabolic needs due to marked growth of the foal in the last three months of gestation. Additionally, the foal will occupy a great deal of space in the abdomen, making consumption of large quantities of forage needed to meet metabolic demands difficult. Therefore, mares in the last trimester of pregnancy may need as much as 1 to 1.5 percent of their feed requirement in the form of grain or concentrate.
Lactation also places a great deal of strain in some mares, requiring further increases in feed and concentrate during the first couple of months of lactation. This is an important consideration and you should plan ahead to avoid sudden feed increases once lactation starts.
Many mares are often expected to become pregnant again right after foaling, and conception may be difficult or impaired if the mare loses excessive body condition while nursing the newborn foal. In any case, remember that each horse is an individual and generalizations cannot be made.
For any horse, sudden changes in diet should be avoided. This may predispose to gastrointestinal upset and colic. Any changes or upgrades in diet to meet requirements for late pregnancy or lactation should be done gradually, over a period of two to four weeks.