Breeding and Foaling Basics: Gestation, Due Dates and Coat Color
Breeding a mare is a big commitment. This guide explains how gestation is counted, how to estimate a foaling date, what normally happens at foaling and how coat color is inherited.
Gestation length
A mare carries a foal for about 340 days, or about 11 months. The normal range is wide, from about 320 to 370 days or more, and healthy foals are born at both ends. Mares that foal in spring often carry slightly longer than those that foal in late summer. Individual mares tend to repeat their own pattern from year to year. The Foaling Date Calculator adds 340 days to the breeding date and shows the range, so you know when to start watching.
| Milestone | Approximate timing |
|---|---|
| Pregnancy check by ultrasound | 14 to 16 days after breeding |
| Heartbeat confirmed | About 25 days |
| Vaccinations and deworming plan | Per your vet, usually in the last trimester |
| Watching closely | From about day 320 |
| Expected foaling | About day 340 |
Preparing the mare
- Keep her in condition 5 to 6 on the Henneke scale; see Body Condition Scoring.
- Increase feed quality in the last trimester, when the foal grows fastest; see Feeding Horses.
- Follow your vet's vaccination and deworming advice; some products are not safe in pregnancy.
- Provide a clean, large, well-bedded foaling stall or a clean small paddock.
Signs foaling is near
- The udder fills (bagging up) in the final weeks, and wax appears on the teats within days of foaling.
- The muscles around the tailhead soften.
- The mare may become restless, sweat, pace or lie down and get up.
The 1-2-3 rule
A normal foaling is quick, and the rule gives you a way to know whether to call the vet.
- 1 hour: the foal should stand within about an hour of birth.
- 2 hours: the foal should nurse within about two hours.
- 3 hours: the mare should pass the placenta within about three hours.
The active stage of labor normally takes 20 to 30 minutes after the water breaks. Call a vet immediately if there is no progress after 20 to 30 minutes of hard labor, if you see a red bag instead of a white membrane, if the foal is presented abnormally, or if any of the 1-2-3 times is missed. Have the vet's number ready.
Care of the newborn
Check that the navel stump is treated as your vet advises. The foal needs colostrum, the mare's first milk, within the first hours of life, and a vet may recommend a blood test around 18 to 24 hours to check antibody levels. Watch for a foal that is weak, will not nurse, has a swollen joint or has not passed meconium within the first day.
Coat color basics
Horse coat color comes from a small set of genes. The base colors are black and red (chestnut), and other genes modify them to produce bay, buckskin, palomino, grey and many others. Because red (chestnut) is recessive, two chestnut horses can only produce a chestnut foal, while a bay can carry the red allele, for example. Some colors, such as grey, depend on one dominant gene, and others need two copies. Testing is the only sure way to know what a horse carries. The Foal Color Calculator estimates likely colors from the parents' colors and any known genotype. Remember that the real outcome depends on the genes a given horse carries, and that coat color is only one of many reasons to choose a stallion.
Should you breed?
Breeding costs money in stud fees, vet care and feed, and many foals are hard to place. Consider the mare's soundness and temperament, the market, and your ability to care for a foal for years. The Should I Breed My Mare Finder walks through the questions to ask, and the Horse Name Finder helps with the fun part afterward.
Common mistakes
- Treating 340 days as an exact due date.
- Not watching a mare closely after day 320.
- Waiting too long to call a vet when labor stalls.
- Assuming a coat color calculator is a guarantee.
Frequently asked questions
How long is a horse pregnant?
About 340 days, or roughly 11 months, with a normal range of about 320 to 370 days.
What is the 1-2-3 foaling rule?
The foal should stand within 1 hour, nurse within 2 hours and the mare should pass the placenta within 3 hours. If any of these is missed, call your vet.
Can two chestnut horses have a bay foal?
No. Chestnut is recessive, so two chestnut parents can only produce a chestnut foal, apart from rare exceptions and other color genes.
Tools used in this guide
More guides
- Feeding Horses: Hay, Grain and Supplements
- Body Condition Scoring with the Henneke Scale
- How to Estimate Your Horse's Weight Without a Scale
- Deworming Strategy for Horses: Fecal Egg Counts and Targeted Treatment
- All HorseCalcs guides
Figures in this guide are general guidance for planning. Every horse is different, so work with your veterinarian, farrier or trainer on health, hoof and training decisions, and read our disclaimer.