Fetal Programming

The term ‘fetal programming’ may sound like it belongs in a science lab rather than a breeding operation, but this concept is something that breeders should take note of. Most people don’t realize it, but a developing fetus can actually adapt to external factors while in the mother’s womb, and those adaptations have a life-long effect on the baby. Development of a fetus is a complex process that is often taken for granted by equine breeders. Even though the growing fetus is protected deep inside of the mare’s abdomen for 11 months, development can be effected by nutrition and stress factors from the outside world.

Modern equine athletes are pushed to the highest extremes at young ages and then expected to continue careers well into their late teens and even twenty’s. The interesting aspect of fetal programming is the life-long effects on offspring. Since the future health and soundness of a horse truly begins before birth, fetal programming deserves attention from the equine breeding and performance industry. Dr. David Barker, pioneer of fetal programming, stated “the nourishment a baby receives from its mother determines its susceptibility to chronic conditions later in life”. Little research has been published on fetal programming in horses, however abundant research is available in humans and other animal species, so we expect that horses follow the same patterns.

Researchers from the University of Cambridge compiled a list of studies showing nutrition of the mother during pregnancy has a direct effect on her offspring later in life. Low protein diets resulted in anxiety behaviors, hypertension, impaired spatial memory, insulin resistance, altered glucose metabolism, renal dysfunction, and impaired immunity. Undernutrition in general caused vascular dysfunction, altered brain function, cardiac remodeling, obesity, hypertension, glucose intolerance, and impaired cognitive performance. Take a moment to consider how some of these life-long conditions such as anxiety, impaired memory and altered brain function could be detrimental to the training program of a young colt. When horses are paid up at high stakes even the smallest level of anxiety or a mental breakdown can be costly.

Undernutrition during pregnancy followed by excess nutrition after birth can lead to development of metabolic syndrome. This is particularly interesting considering rates of Equine Metabolic Syndrome (EMS) are increasing in horse populations. Equine Metabolic Syndrome is characterized by obesity, insulin resistance and laminitis in horses, and is very similar to metabolic syndrome in humans. Certain horse breeds and genetic bloodlines are more likely to develop EMS, but fetal nutrition may also play an important role. When there is stress on the fetus caused by undernutrition of the mother, the developing fetus reprograms itself to favor immediate survival. However, this adaptation causes metabolic disease for the offspring later in adult life, according to a 2013 study published in Reviews in Endocrine and Metabolic Disorders. For horse breeders producing genetic lines known to develop EMS, this is valuable information for management because the default might normally be to reduce the plane of nutrition for the mare, but that could actually be compounding the problem for the offspring.

Since the fetus makes adjustments according to the mother’s nutritional status, breeding managers should provide mares an adequate plane of nutrition from conception through parturition and lactation. An all too common practice for breeding operations is to confirm pregnancy in a mare, then turn her out to pasture or be placed on a hay-only diet for the majority of her pregnancy. During this period of gestation where the mare is “out being a horse” the fetus may be in an “undernutrition” state due to a lack of certain nutrients. The common practice of bringing the mare in for foaling and feeding her a fully fortified feed during lactation then creates a mismatch between pre and postnatal environment. When there is deprived nutrition (during pregnancy) followed by adequate nutrition (after birth), catch-up growth occurs which may cause development of diseases such as glucose intolerance, obesity and laminitis later in life.

As more equine research unfolds regarding fetal programming it will be interesting to follow the advances in equine nutrition. Right now breeders and horse owners should consult with an equine nutritionist to ensure proper levels of macronutrients and micronutrients are being supplied in the diet of broodmares, donor mares and recipient mares even before conception. Then, an adequate plane of nutrition should be maintained for the mare carrying the fetus throughout the entire pregnancy and during lactation in order to provide her foal with the best chance at a long and healthy life.