Feeding Broodmares for Conception

Dr. Tania Cubitt

Performance Horse Nutrition


Mare owners spend thousands of dollars on stud fees and shell out hundreds of dollars in veterinary care to prepare their mares for breeding and foaling. Mares are expected to grow a healthy foal inside them for 11 months and produce enough milk for that foal for up to 6 months. Furthermore, many mares are expected to raise healthy foals year after year, requiring successful rebreeding while the previous year's foal is still by her side. Because nutrition influences each stage of the broodmare's production cycle, nutritional management may, in many ways, determine the success of the breeding program.

Broodmare nutrition can be broken down into several different stages: conception, early, mid and late gestation, and lactation. In this article we will focus on nutrition for improving conception. Nutritional management is a simple yet cost effective tool that we can apply to ensure normal reproductive cycles, improved conception rates and increased pregnancy maintenance in mares to ensure overall reproductive success. 

Body Condition

The effect of nutrition and body condition on reproduction in mares has been clearly illustrated.  Mares coming into the breeding season with an optimal body condition score (5-7) start cycling earlier than mares with a low body condition (less than 5). Thinner mares also have difficulty conceiving and maintaining pregnancy as compared to mares in optimal body condition. Some obese mares continue to cycle throughout the winter when typically, reproductive cycling is shut down.  The impact of energy intake and body condition on the reproductive performance of the mare has also been described where a high-energy diet shortened the interval to first ovulation in thin mares transitioning from winter as compared to those on a low energy diet.  This increase in dietary energy however does not benefit mares that are already in an optimal or fat body condition.

While some obese mares may continue to cycle throughout the winter there are negative repercussions for keeping mares in this condition.  In humans and rodents obesity contributes to infertility, poor pregnancy and impaired fetal well-being.  Obesity has been associated in horses and ponies with decreased insulin sensitivity, and both obesity and decreased insulin sensitivity have been associated with decreased reproductive function in mares.  Obese mares can have a longer interval between ovulations which can be due to a persistent corpus luteum.  This makes the obese mare more difficult to rebreed if an initial breeding is not successful increasing the cost incurred to the owner.

Mares in optimal body condition going into the breeding season typically do well on good quality forage and a concentrated vitamin and mineral pellet. If mares are overweight prior to the breeding season a combination of a ration balancer and exercise is an ideal program to get them into optimal shape before breeding. If the mare is underweight a high fat feed with highly digestible fibers will help increase the mares’ body condition in preparation for breeding.


The major vitamin of concern during pregnancy is vitamin A. Vitamin A requirements are doubled when mares are in late gestation and lactation. It is important that the supplement contain at least 10 to 1 ratio of Vitamin A to Vitamin D, a 6 to 1 ratio of Vitamin D to Vitamin E, and be fed at levels recommended on the label.


Research into chelated minerals for horses has focused on the broodmare and the young growing horse.  Studies have shown that mares receiving trace mineral supplementation in a chelated form had a tendency for a reduction in the number of cycles bred and in the number of services per mare. However, conception rate was not measured (Ott & Asquith, 1994). Other researchers have suggested improvements in reproductive performance in barren or open mares by reducing time to first cycle or reducing early embryonic loss when chelates were fed (Ley et al, 1990).

In the growing horses the addition of a chelated mineral product which supplied a portion of copper, zinc and manganese as chelates resulted in an improved hoof growth for the yearlings receiving that diet. There was no increase in strength of the hoof wall but growth was enhanced. Similar results have been reported with dairy cattle fed chelated products (Ott & Johnson, 2001).

Studies have examined immune function in foals from dams fed inorganic or chelated minerals during late gestation. Foals born to mares fed chelated minerals had increased immunity at birth compared to those from mares fed inorganic trace minerals during gestation (Vickers et al., 2009a). Additionally mares supplemented for 9 months with chelated minerals developed more follicles post partum than mares only supplemented for 3 months (Vickers et al., 2009b).

It is important that each mare be treated individually, make sure you monitor changes in body condition weekly and make feeding changes accordingly. Supply the mare with plenty of good quality forage along with the correct product and you can be rest assured her nutritional program has been well taken care of. Dac Vitamins and Minerals offers an excellent vitamin and mineral supplement to improve reproductive success in your mares. Breeders Choice Plus is enhanced with chelated minerals as well as elevated levels of vitamin a and 100% natural Vitamin E.

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