A closer look at the facts behind Thoroughbred breeding frequency, care, and comparison to wild horses.
Critics sometimes claim Thoroughbred mares are overbred – but the reality is that Thoroughbred breeding aligns with a mare’s natural biological cycle.
How often are Thoroughbred mares bred?
Mares in professional breeding programs are typically bred once per cycle – just like wild mares do when conditions are right. The mare needs to be in the precise right time in her ovulation cycle.
-
Breeding season: In the Southern Hemisphere, this runs from September to December.
-
Natural cycles: Mares cycle every 21 days, with a window of 4–7 days when they are receptive and their follicles are suitable for conception.
-
Vet-led timing: Ovulation is monitored via ultrasound, and mares are covered only when optimal, often just once per cycle.
That’s in sharp contrast to the wild, where a stallion may cover a mare repeatedly – sometimes four times – in one cycle. Thoroughbred mares are not exposed to that same level of physical stress.
Is breeding harmful to the mare?
No. The health of the mare is the foundation of every breeding operation. If she’s stressed, injured or not thriving – she won’t get in foal or carry to term.
Welfare measures include:
-
Purpose-built breeding sheds: With safe footing and low-stress environments.
-
Trained staff and veterinarians: On hand for every session.
-
Protective equipment: Like breeding boots and hobbles to protect both horse and human.
-
Minimal covers: Thanks to ovulation tracking, most mares are only bred once per cycle.
How many foals does a mare have?
Most mares will produce 8–12 foals in a lifetime.
-
They usually start breeding at 3–4 years old.
-
Many are retired by their late teens.
-
While the record is 17 foals (Guinness World Records, 1998), that’s the rare exception – not the norm.
Can a mare get time off?
Absolutely. In fact, it’s not uncommon for mares to skip a season. Reasons include:
-
Health recovery after foaling.
-
Fertility support to give them the best chance of success next year.
-
Late foaling so they don’t get out of sync with the seasonal calendar. Because mares are in foal for 11 months and 11 days, if they get in foal too late then the foal will be born late in the season. Sometimes a year is skipped, so the mare can be covered early the following season.
Wild mares vs. breeding farm mares
In the wild, mares tend to have one foal a year, but only if nature’s conditions allow. According to the Bureau of Land Management (2017), wild herds have an annual foaling rate of 60–75%, but face:
-
Repeated matings each cycle, which can be stressful.
-
Environmental threats like food shortage and predators.
-
High pregnancy loss due to poor nutrition and stress.
Thoroughbred mares, by contrast, live in highly controlled environments where nutrition, health, and timing are all optimised to support conception, foaling and mare health.
Final word
Thoroughbred mares are bred once per cycle, on schedule with ovulation, and under expert supervision. Compared to wild mares – who face repeated mating, resource scarcity, and no veterinary support – the breeding process on farms is designed to safeguard both the mare’s welfare and her long-term reproductive health.
