We looked at the stallion’s diet last week, and this week it’s the turn of the pregnant mare, whose diet needs to change in the final three months of gestation in order to maximise the health of the foal as well as to support her own health.

The pregnant mare’s nutrient requirements are not much higher than those at maintenance during her first 5 months of gestation, although care should be taken to supply enough vitamins and minerals. Requirements rise gradually from month 5, and significantly in the final 3 months. Her diet should be changed accordingly, with attention paid to grass availability, which will have a big impact on what concentrate feed she needs (or not). Mares fed forage only e.g. on spring grass, still need to have mineral supplementation.

In the final 3 months of gestation, the growing foetus not only requires adequate minerals for ongoing development, but must also lay down body stores for use during lactation, because mare’s milk does not supply adequate levels. It is vital, therefore, to feed a multi-vitamin and mineral supplement to all late-gestation mares who do not require the full recommended amount of fortified compound feed.

Spring pasture is an ideal feed for mares in late pregnancy and lactation.
Spring pasture is an ideal feed for mares in late pregnancy and lactation.

Energy requirements of the mare gradually increase to 28% above maintenance in the final month of pregnancy, but the mare should be assessed individually and fed accordingly. If a mare is out on spring grass during her final few weeks, this can be an ideal way of meeting increased requirements. Do not overfeed and allow the mare to get too fat, because this can lead to complications at foaling. Overfeeding energy in late gestation does not increase the foal weight at birth, and instead causes fat gain in the mare.

Protein requirements rise from about 630 g at maintenance to 890 g at month 11 for a 500 kg mare. The quality of protein is important and if the mare doesn’t need much compound feed to maintain weight, then a balancer product supplying good quality protein as well as vitamins and minerals should be fed.

Supplementary vitamin E and selenium during the final 3 months has beneficial effects on the transfer of immunity to the foal after birth via the colostrum. Total diets should be about 2000 mg of vitamin E (200 mg/kg diet dry matter) and 3 mg selenium (0.3 mg/kg diet DM), based on a 500 kg mare.

Grulla Spanish Mustang in foal.
Grulla Spanish Mustang in foal.

Mares bred very early in the year, who are in late gestation in mid to late winter may require the full recommended amount of compound feed, particularly if the forage is not of high nutritional quality. For good doers, ponies and any other mares who maintain weight in the final months of pregnancy on good quality forage-based diets, do not be tempted to feed them stud mix compounds, but instead feed a good multi-vitamin and mineral supplement.

Mares should ideally be kept in the environment in which they are to foal for a few weeks prior to the foaling dates to allow them to produce relevant antibodies that they can pass onto their foals in the colostrum.

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About Clare MacLeod

Clare MacLeod MSc RNutr is one of the UK’s few registered independent equine nutritionists who also has expertise in health and fitness. She advises private and commercial clients in all sectors of the horse world and is a hands-on horse owner herself. Clare is passionate about correct nutrition as a foundation for good health, without which peak fitness is not possible. She states “Good nutrition isn’t everything, but there’s nothing without it”.