A broodmare is a female horse kept specifically for breeding. She may have been retired from competition, selected purely for her genetics, or purchased as a proven producer — but her primary role is to produce foals that inherit her qualities and those of the stallions she is bred to. Broodmare management is a specialist field within horse breeding, requiring knowledge of reproductive physiology, nutrition, and neonatal care.
Selecting a Broodmare
The quality of the broodmare is widely considered to be the single most important factor in a breeding programme. Breeders evaluate candidates across several criteria:
- Conformation: Structural correctness reduces the likelihood of passing on conformational faults to offspring. A mare’s conformation is scrutinised particularly around the pelvis (critical for ease of foaling), limbs, and overall balance.
- Bloodlines: Pedigree analysis informs nick predictions — certain sire and dam lines produce consistent results when combined. In Thoroughbred and Warmblood breeding especially, bloodline analysis is a serious science.
- Performance record: A mare that competed successfully at a high level provides evidence that her genetics produce athletic ability. In sport horse breeding, performance records are weighted heavily in breeding value assessments.
- Temperament: Difficult temperament is heritable. A mare that is anxious, reactive, or difficult to handle is more likely to produce foals with similar characteristics — and her own behaviour in the paddock and foaling box affects foal imprinting and early development.
- Reproductive soundness: Prior to inclusion in a breeding programme, mares should be examined by a reproduction specialist. Uterine health, cycle regularity, and prior foaling history all inform the likelihood of successful conception and foaling.
The Breeding Season and Reproductive Cycle
Mares are seasonally polyoestrous — they cycle naturally in spring and summer, driven by increasing day length. In the UK, the natural breeding season runs approximately from April to October, with peak fertility in May to July. Most horse breeds follow this pattern, though artificial lighting programmes can advance the onset of cycling for Thoroughbred breeding, where all racehorses have a universal birthday of 1 January and early foals are advantageous.
Mares can be bred by natural cover (live cover with a stallion) or via artificial insemination (AI) using chilled or frozen semen. AI has become increasingly prevalent, allowing access to the genetics of stallions worldwide without the cost or stress of transporting a mare. The FEI and most breed societies have established rules around the use of AI in competition breeding programmes.
Broodmare Care and Management
A pregnant mare’s nutritional requirements increase significantly in the last trimester — the final three months of the 11-month gestation period is when the majority of foetal growth occurs. Energy and protein demands rise, and supplementation with specific vitamins and minerals (selenium, vitamin E, and omega-3 fatty acids in particular) supports foetal development and colostrum quality. Over-conditioning in late pregnancy, however, creates foaling difficulties and metabolic problems — body condition should be monitored closely.
Foaling mares require close supervision, particularly at night when most foals are born. Signs of imminent foaling include waxing of the teats, muscle relaxation around the hindquarters, and behavioural changes such as restlessness and pawing. Most mares foal without difficulty, but complications such as dystocia (abnormal foal presentation) require immediate veterinary intervention. A foal that has not stood and nursed within two hours of birth warrants a veterinary call.
Frequently Asked Questions
At what age can a mare start breeding?
Mares can physically be bred from two years old, but most reputable breeders wait until three or four. Breeding a two-year-old places significant physical demands on a body that is still developing, and early pregnancy can affect the mare’s own growth and musculoskeletal development. Sport horse mares are often not entered into breeding programmes until their competitive career winds down, commonly in their late teens — provided their reproductive system remains healthy.
How long is a mare pregnant?
The average gestation for a horse is 340 days, or approximately 11 months, though normal gestation ranges from 320 to 370 days. Foals born before 300 days are considered premature. Mare owners typically begin monitoring closely from day 320 onward. There is no reliable method of inducing labour in mares without veterinary involvement, and attempts to do so without good reason carry significant risk to the foal.
Can a mare be bred every year?
Biologically, yes — mares can theoretically produce one foal per year. In practice, responsible breeders assess each mare’s condition and reproductive health before deciding whether to breed in consecutive years. Mares that foal and are immediately rebred (foal heat breeding, which occurs roughly seven to nine days after foaling) carry higher early pregnancy loss rates compared to mares given a rest cycle. The mare’s welfare, age, and condition should always take precedence over breeding scheduling.