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Not every mare that’s bred is able to become pregnant in a particular breeding season. While broodmare managers on large commercial horse farms are able to accept this reality, owners with only one or two mares can easily end up with a zero percent success rate for the season. What factors can derail a breeding, and how can the mares be managed for a more positive result in the future?

Getting mares ready to be bred is not an overnight chore. An owner who is considering breeding a mare needs to begin several months ahead of the breeding season in order to have the mare in the best condition to become pregnant. The first step is to have a veterinarian examine the mare for breeding soundness. This should be done in plenty of time to treat or correct any problems that may be found.

The veterinarian will evaluate the mare’s conformation and internal reproductive organs to check for infection or damage from previous pregnancies. Using the mare’s breeding history, he can suggest management steps to avoid problems. Maybe the mare needs to be put under lights, or bred by live cover rather than artificial insemination, or examined for conformation defects such as a tipped vulva that can increase the risk of uterine infection. The veterinarian may also find a condition that would make it unwise to try to breed the mare, saving the owner time and expense and allowing another mare to be chosen for breeding.

Mares selected for breeding need to be in excellent physical health and should be on a regular course of hoof care, immunizations, parasite control, and dental care. This schedule of routine health care needs to be in place in the months leading up to the breeding season. A mare that has been neglected, is seriously underweight, or is in the process of recovering from a major illness or injury is less likely to get in foal and deliver a healthy baby eleven months later. Prospective broodmares should also be sound enough to carry the extra weight of a foal without experiencing significant discomfort.

Nutrition of the prospective broodmare is important for a successful breeding. Mares that are either too thin or too fat may be difficult to get in foal and stay in good condition through the pregnancy. For optimal breeding efficiency, mares should have a body condition score of at least 5 to 6. According to Henneke’s nine-point body condition scale in which 1 is emaciated and 9 is obese, a 5 represents moderate body condition. The back is level with no crease or ridge, ribs cannot be seen but can be felt, tailhead is surrounded by a layer of fat, withers are well-rounded, and neck blends smoothly into the shoulder.

Research has shown that barren mares kept at a body condition score of 5 begin ovulating sooner than mares with body condition scores less than 5. These mares also require fewer estrus cycles to achieve pregnancy and generally have higher conception rates. Mares that enter the breeding season in very thin condition are less reproductively efficient than those in moderate body condition.

Some broodmare managers like to keep their mares just slightly over moderate condition, while others prefer to have the mares come into the breeding season just below moderate condition. These mares are then fed enough hay and grain to be gradually gaining a bit of weight for a while before they are actually bred, a strategy that tells the mare’s body that she is ingesting enough nutrients and energy to support a pregnancy. Both plans work for many mares if sufficient time is allowed for under-conditioned horses to reach moderate body condition.

In general, access to top-quality forage will help thin mares gain weight. If forage alone does not provide enough calories for weight gain, a well-formulated concentrate should be offered, following the manufacturer’s instruction printed on the feed bag or tag. First-time breeders might want to consult with an equine nutritionist as to the best overall plan, especially if the mare has a particular condition that requires special feed ingredients or schedules.

Choosing the stallion is an important step toward a successful breeding. Live cover usually has a good rate of settling mares in foal, but this option may involve the stress of transporting the mare for a long distance. If artificial insemination (AI) seems to be the best alternative, the mare’s owner needs to ask about conception rates from chilled or frozen/thawed semen, as some stallions have far more success than others. It’s also important to have the help of a veterinarian who is experienced in AI procedures.

The important thing about all the steps in readying a mare for the breeding season is to start early enough that any defects and problems can be discovered and resolved well before the proposed breeding date. Having a reasonable timetable is essential for all prospective broodmares, but is especially vital if the mare has a history of difficulty in becoming pregnant or sustaining a pregnancy to term.

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