Broodmares - To Supplement or Not to Supplement? 

When your mare is in foal and supporting the development of a new life, it stands to reason, she needs an increase in energy and nutrients both to maintain her health and to support the growing foal. Many owners allow their pregnant mare to remain at pasture, grazing freely. Therein lies the question, is it always necessary to supplement the diet of a mare at pasture, or can pasture grazing alone provide her with all her nutritional needs? Let's find out more

How Much Grass is Genuinely Enough For A Broodmare?

How much should I feed my broodmare
The lactating mare needs extra nutrition to properly provide for her foal*

Pregnancy and post foaling lactation, are the most demanding periods in terms of energy and nutritional needs, known to the mare. As you probably know, grass quality, nutritional value and energy content can vary. While equine nutritionists have indeed confirmed that it is possible for a mare to receive complete nutrition from pasture grazing alone, the quantity of grass the mare requires is the bigger concern. To produce sufficient quantities of nutrient rich milk during the lactation period, the mare can require as much as a 44% increase in energy intake. So, how do we determine that the mare can indeed reap sufficient nutrition from pasture alone or that her diet must be supplemented to correctly meet her needs?


French Researchers Answer The Question.

So, how much grass does a mare need to sustain her energy requirements, before requiring supplementation? A French team set about conducting the necessary experiments to get answers to this very worthwhile question.

It was determined that a mare, strip-grazing with a 1- to 4-month-old weanling foals should be changed to high-quality pasture strips every two days. When following this regimen, the mare will require access to 66 grams of dry material (grass) per kilogram of body weight per day. This would mean that over a day, a mare must have access to roughly 39 kilograms (or 85 pounds) of grass to meet their nutritional needs.
It is important to note that this is not the amount the mare must eat but will require access to. Pasture is naturally exposed to damage from hooves, being covered over in droppings and/or fallen leaves or may be too short to graze. Therefore a proportion of the pasture will not be accessible to the mare. For the average owner or breeder, figuring out these measures may seem fairly daunting? Fortunately, the researchers recalculated the numbers so that lay persons could apply the equation, fairly accurately.

Getting the Numbers Right so Your Mare is Fed Correctly.

According to the study, the best way to monitor your mare at home is to keep tabs on grass height. Allow the mare and foal access to pasture and after two days of grazing, check the height of the grass. If the mares are leaving 5 centimeters (about 2 inches) of grass or less, then the grazing should be increased or a supplement should be added.

A study previously carried out by the same team determined that lactating mares on pasture grass of high quality required no additional feed to meet their nutritional needs. However, this latest study has investigated the more realistic situation of normal pasture with limited grass yields. It was found that all the mares in the study spent less time grazing when the grass was around 5cm. Once grazed below 3cm, the time was reduced even further. When reviewing the feces of the horses to study digestibility of these shorter grasses, the researchers determined that the horses were ingesting less overall dry material on the lower-length grasses compared to what was ingested when horses were allowed to consumer medium-length grasses. There was also a corresponding increase in consumed roughage when horses grazed on higher length grasses.


At present, this information is useful as a starting guideline for mares, but further research is still needed. Being able to gauge pasture types, the impact of seasonal changes, etc. is critical to accurately determine when best to supplement broodmares pasture grass consumption.

 *Image courtesy of Dollar Photo Club