Breeding Season: Choosing The Right Month For Your Mare

Last Updated on September 3, 2021

What is the best month to breed a horse? You’ve finalized your decision to breed, you’ve picked your stallion, and now it’s time to pick the exposure date! Is there really a “perfect” month? Although the timing is essential for insemination, the season is dependent upon each unique situation. When deciding what is the best month to breed a horse, consider these four factors before moving forward:

Factors To Consider – What Is The Best Month To Breed A Horse


Geographic location largely impacts the ideal breeding month. When examining a horse’s natural reproduction system, early summer and spring insemination typically results in more hospitable environmental conditions- increasing a foal’s natural survival rate.

Although late winter or very early spring breeding might sound appealing, foaling facilities and veterinary assistance remain an important factor. If a region is susceptible to heavy snow and ice or a particularly violent storm season like tornadoes, beginner breeders will want to ensure their regional weather will likely permit vet travel.

What is the best month to breed a horse - Weather

Although most experts agree outdoor foaling is the healthiest option, weather restrictions during winter and spring may call for secondary facilities, such as a prepared foaling stall.

Mid to late summer breeding may seem ideal when considering weather for the birthing process. However, mares are pregnant on an average of 11-12 months. This means the latter part of her pregnancy may be spent in unseasonably warm temperatures, creating discomfort and possibly a more complex weaning scenario in the winter.


If the future foal is slated for competition, birthdate can matter. Many breed registry organizations assign January 1st as an official “foal” date. This means a horse born in January would be competing against a horse born in August as a “yearling” the following year and held to the same standards. Early season foal births have obvious advantages in the show ring when competing in age division categories. 

Natural Cycle

A mare’s natural heat cycle typically ranges from late spring (late April or early May) to late summer (August). This time period is typically when the most regular and standard 22-day estrus cycle occurs, resulting in the highest probability of conception.

Mares will enter anestrus during winter months, which results in a transition period during the spring. This means mares do not always jump into a regular heat cycle, so early breeding frequently requires the use of artificial sunlight. Like winter coat growth, estrus cycles are directly affected by sunlight hours. Progesterone or oxytocin might also be used depending on the circumstances of the breeding and degree of cycle manipulation.

Booking Requirements

It takes two to tango! Unfortunately, breeding is not always as simple as examining your own circumstances. Whether booking a stallion for pasture exposure many stallion owners have seasonal restrictions for collection or stud services. Although research has shown hot weather does not negatively impact stallion fertility (Cavinder), transport most certainly plays a role in sperm viability. If you are shipping a long distance, consider the outside temperatures when making arrangements.

Final Words – What is the Best Month to Breed a Horse

While there may not be the “perfect” month to breed, these guidelines will help you better understand what goes into the decision-making process. Despite the stressors that may come with breeding- the end result is well worth the time effort! 


How Do Mares Behave In Heat?

In spring, or what the horse industry refers to as breeding season, it is common to see behavior changes in a mares disposition. When a mare is in heat, it is very common for them to have an undesirable attitude. It is very common for a mare to squeal and become distracted by other hoses.

Other signs your mare is in heat may include tail raising, winking, and frequent posturing and urination. Some mares may also become very vocal and anxious, while others may become aggressive. During this time mares also may seem a bit lethargic and reluctant to work, this could be partly because of the increased sensitivity and pain that can occur in and around the flanks. 

How Many Mares Can A Stallion Breed In One Season? 

The number of mares a stallion can breed in one season will vary based on the age of the stallion. At the age of two a young stallion can breed 6 to 10 mares, at age three 10 to 15 mares, at maturity 50 to 60 mares, and in their senior years’ age twenty – twenty-five they can cover 30 to 40 mares.

During the breeding season if you have a stallion turned out to pasture with the mares during the breeding season he should be able to successfully breed 50 mares. Hand mating is also used at many breeding farms. This method has the potential to increase the number of successful breedings to 100 and sometimes more. Now the number of successful breeding can increase if artificial insemination is used. With an AI program anywhere from 70 to 2,450 mares can potentially be bred by one stallion. 

How Many Times Can A Stallion Breed In One Day?

When a stallion is turned out with mares for pasture breeding, he will mate much more than 2 or 3 times per day. Successful breedings for a stud that is age 2 or older and has been through a few breeding seasons will be able to cove 2 to 4 mares in one day. To have successful conception rates (aka covering) with breeding multiple times per day, it is best to allow the stallion to rest and spread the breedings throughout the day. Breeding more often either multiple times in one day or at least every other day will keep the sperm count levels high, unlike breedings that are days apart which will cause a significant decrease in the stallion’s sperm count. 

At What Age Do Mares Stop Going Into Heat?

Most mares begin to have irregular heat cycles in their early twenties. It’s common for many mares to no longer have a heat cycle around 25-28 years of age, but it is not uncommon for mares well into their 30s to still come into heat. A mares fertility will begin to decline between the ages of 15-20. As fertility declines the heat cycles will diminish also, if the mare is no longer ovulating the need for a mare to have a heat cycle is no longer necessary There is no exact age when a mares heat cycle fully goes away, as it will be different for every horse.