An enormous amount of attention is devoted to what pregnant women should and shouldn’t eat and to suitable vitamin and mineral supplements. Undernutrition during pregnancy is known to have a detrimental effect on the health of the offspring in most species — including horses.
For most mares in the UK, however, there is probably a greater risk of owners overfeeding their mares. Because most of the foal’s growth occurs in the last third of pregnancy, a mare’s nutritional requirements until that time do not differ significantly to those of a non-pregnant mare.
A 2012 study published in The Veterinary Record, by Van der Heyden et al, shows that nutrition during pregnancy has a significant effect on whether or not a foal develops osteochondrosis (OCD), which is a form of developmental orthopaedic disease.
These study results should be interpreted with caution, because no data was available about the composition or the quantity of the foodstuffs being fed to pregnant mares. But the overall conclusion supports the claims of previous research — that overfeeding of concentrates to mares during pregnancy is detrimental to the orthopaedic health of their offspring.
The message for owners to take from this is that pregnant mares should have a high-forage diet supplemented by the correct balance of vitamins and minerals, which are available in commercial form from most of the large feed suppliers. She should not be overfed protein or starch, or allowed to become overweight.
To read all the latest mare research and developments see the current issue of H&H (25 April 2013)