You are what you eat certainly applies to horses, and may even apply to what their mothers eat. Maternal nutrition and fetal programming was the subject of the Equine Species symposium at the Joint Annual Meeting of the American Society of Animal Science this past July, and the review paper, Nutritional programming and the impact on mare and foal performance, prepared by Josie Coverdale and others at Texas A&M University was published in the corresponding Journal of Animal Science (doi:10.2527/jas.2015-9057).
While under-nutrition can certainly have detrimental effects on the foal, the authors highlight the impact of over-nutrition of the mare in today’s industry, as many mares are fed diets rich in concentrates (and starches and sugar) and are fed to be over-conditioned (body condition score >6/9 scale).
Overfeeding the mare to 120% of her energy requirements using grain to supplement the diet, during the last 110 days of gestation didn’t affect foal birth weight or time to stand and nurse, but did result in lower colostrum immunoglobulin (IgG) concentrations and lower serum IgG concentrations.
These authors also discuss their work in which supplemental selenium or arginine did not return IgG concentrations to control values. Work in horses has also shown that overfed mares affected glucose and insulin dynamics in the foal, which may potentially lead to insulin resistance as an adult (similar to human babies born to obese mothers).
The work conducted in this field opens up a series of questions regarding the impact of maternal nutrition on the future health and performance of the foal.