Regardless of general feeding guidelines for breeding horses, body condition score (BCS) is the most objective assessment of a horse's fat covering and also the best predictor of reproductive performance or efficiency. Breeding horses should be maintained at a BCS of 5-6 (on a 1-10 scale), where ribs are invisible but readily palpable. Most horses should be offered 2-3% of their body weight per day in dry matter (forage and concentrate combined) and should consume 5.5-11 gallons of free-choice water.

Breeding Stallions

Reproduction is an athletic event. In other words, breeding horses that are athletic will maximize their breeding efficiency. The National Research Council suggests nutritional needs of the stallion during the off-season are no different than those of the nonbreeding horse, and during the breeding season his caloric demands only increase by 1.25 times.

Provide stallions with a trace mineral supplement block versus a salt block manufactured for rough-tongued ruminants. As with horses of all genders and uses, the breeding stallion should be fed a forage base with caloric enhancement using grains (carbohydrates) or fat supplements.

Always feed a breeding stallion high-quality hay. As hay ages, it becomes less digestible because of increased lignin (a fiber component) concentrations. Many hay producers cut hay after it is too mature, which will artificially increase the amount of lignin the stallion ingests.

Inactive stallions can gain weight on pasture turnout alone, even if the forage is of average quality. As a matter of academics, it is difficult to find a nonbreeding stallion that cannot be maintained on forage and 6 pounds of grain per day. Fat is becoming more popular as the caloric source of choice for owners concerned about carbohydrate intake, laminitis, hyperadrenocorticism (equine Cushing's disease), polysaccharide storage disease syndromes (such as tying-up), and glycogen storage disease, among others. Remember that horses can easily gain 1.5-2 pounds per day, so those entering the breeding pool from the performance environment can quickly become overweight.

The most revolutionary recent reproductive nutritional research is from Texas A&M University (TAMU) and focuses on a higher ratio of omega-3 to omega-6 fatty acids to improve fertility and sperm survivability during semen cooling and freezing attempts.


Mares that are BCS 5 or higher have enhanced fertility, according to studies from TAMU. These researchers also showed that mares below BCS 5 and gaining weight were twice as likely to conceive. This data appears after casual observation that the practice of flushing, which is common in the dairy industry, would work in the horse. Flushing is the intentional reduction of an animal's weight to create a negative energy balance; when calories are subsequently supplemented, fertility rises appreciably. Scientifically, flushing works, but it is inefficient to have your mare's weight fluctuate so wildly, and it might inappropriately stress the horse and, in turn, make her inefficient. A horse is not going to reach maximum efficiency if weight fluctuations have to be overcome.

Similar to stallions, pregnant broodmares should be fed the same amount as nonpregnant mares. In the last trimester of gestation (Months 9, 10, and 11) the energy requirements increase by 1.1, 1.13, and 1.2 times, respectively. Not until late lactation does the nutritional requirement for a mare approach 1.25 times that of a nonpregnant mare. Assuming a foal weighs 9-10% of the mare's weight, and the placenta and fluids weigh about 44 pounds (20 kg), a mare should only gain about 143 pounds (65 kg) and up to 200 pounds (91 kg) during pregnancy.

Foals from obese mares do not tend to differ in birth weight or time to standing, but most experts prefer to have mares between BCS of 5 and 7 before the end of gestation. Underfeeding a mare, on the other hand, could extend gestation by four to 10 days, note TAMU researchers.

About the Author

Benjamin Espy, DVM, Dipl. ACT

Benjamin Espy, DVM, Dipl. ACT (boarded in equine reproduction), has practiced veterinary medicine in Texas and Kentucky. He has been licensed to practice acupuncture for nine years and is on numerous AAEP committees and task forces. Espy serves on the alternative therapy committee for the Texas Veterinary Medical Association, and he's an animal treatment consultant for the Professional Rodeo Cowboys Association.

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