The most common mistakes that are made in feeding the broodmare are overfeeding at the beginning of pregnancy and underfeeding while the foal is nursing. The reason for the first mistake is clear: The foal develops very little during the early months of pregnancy, and the nutritional needs of the broodmare don't change much during this time. Adequate grain ration to ensure good condition and good quality roughage are all that's required, unless the brood mare is underweight. If that is the case, this time can be used to bring the mare up to good condition.
At seven months, however, this situation changes, and the fetus begins rapid growth, so only at this point is there a need to adjust the broodmare's feeding program. After seven months, however, she needs supplemental protein and minerals. Trace minerals should also be supplemented. During this time, the fetus begins to store iron, zinc, copper, and manganese in its liver, apparently because the mare's milk does not supply adequate amounts of these minerals to meet the newborn foal's needs. Supplementing with copper, for example, has been shown to reduce the incidence of problems in bone formation in foals.
If the mare begins to get fat in late pregnancy, it's important to switch her to a feed that supplies a larger amount of protein and minerals per pound so that less can be fed per day. Obese mares have more complications during foaling, and it is therefore important to continue to monitor the mare's body condition throughout pregnancy so that appropriate condition is maintained.
After foaling, the mare's food requirements increase dramatically, however, as she is producing milk high in energy content, protein, calcium, phosphorous, and vitamins. Mares usually require up to fourteen pounds of grain a day after giving birth, depending on the quality of the available forage. Calcium and phosphorous, as well as other minerals, and protein and vitamins should be supplemented. Trace mineral supplementation is not necessary, however, after foaling.
Ideally, the increases in feed should begin in the last few weeks of pregnancy, so that there is no deficiency in milk production once the foal arrives. After three to five months, milk production declines, so the mare's grain ration should be reduced at the time so that she does not become obese.