Breeding Calculators

Two tools, and one big decision

The breeding tools estimate dates and genetic probabilities, which helps once you have decided to breed. They do not help you decide whether to. Breeding a mare is a serious commitment of money and time, it carries real risks for the mare and the foal, and the result is not guaranteed to be a horse that is easy to sell or to ride. Talk to a veterinarian who handles reproduction before you decide.

Which calculator answers which question

• When is she due? The Foaling Date Calculator estimates a due date and the key dates in between.
• What color could the foal be? The Foal Coat Color Calculator shows the possible colors and their probabilities.
• Should I breed at all? The Should I Breed My Mare? finder suggests whether to start with a veterinary evaluation.

How long is a mare pregnant?

The average is about 340 days, or 11 months, but healthy foals are born anywhere from about 320 to 370 days. Mares bred early in the year tend to carry longer, and colts often arrive a few days after fillies. A foal born before about 300 days is considered premature and needs a veterinarian right away. A due date is a guide, so plan to watch the mare closely for several weeks on either side.

Color genetics: probabilities, not promises

Coat color follows basic genetics. Each parent passes one version of each color gene to the foal, so a pairing can produce several colors with different odds, and a calculator can show those odds. It cannot tell you what a particular foal will look like, and some patterns and modifiers are harder to predict than others. A foal's color can also change as it grows, so a foal's coat is not always its adult coat.

Before you breed

Ask your veterinarian for a breeding soundness exam, which is the essential first step. Then count the whole cost: the stud fee, veterinary care, the mare's keep, foaling and raising a foal until it is old enough to ride. Think about the market for a foal of that breeding, and about the many good horses already looking for homes. For many owners, buying an adult horse is the cheaper and safer route.

Common mistakes

• Breeding because the mare is a pet. Affection is not a breeding plan.
• Skipping the veterinary exam. Problems found early are cheaper to deal with.
• Counting only the stud fee. The foal's first years cost much more.
• Treating a color estimate as a promise. It shows odds only.