what is a filly horse

What is a Filly Horse?

Do you often go to horse racing or riding events, or have you recently started with horse riding lessons and often hear people use the terms filly, colt, or foal?

If you’re not sure what these terms mean, well, you’ve come to the right place.

The terms foal, filly, and colt are used to describe horses of a specific gender and age.

In this article, we’ll explain these (sometimes) confusing terms so that, next time someone asks “What is a filly horse?” or “Why do they call it a colt?”, you’ll know the answer.

What Is A Filly Horse?

A filly is a female horse, under the age of four years.

The term filly describes a female horse, between the ages of two and four, and refers to a horse that is not yet fully grown. Once the filly reaches the age of four, it is referred to as a mare.

In the horse racing world, female horses that are younger than five years are referred to as fillies.

Cob tacked up ready to ride

Holly, our beautiful cob. We got her as a 3 year old filly but now she’s 5 and is classed as a Mare

Where Does The Word Filly Come From?

The word filly was first used in the 1500s and comes from the Old Norse word “fylja” which means to follow and was used to describe a young female horse.

Middle English speakers adapted the word to “filli” and used it to refer to a young horse that would always follow its mother wherever she went.

Norse ship on fire. Flames in the shape of a horses head

The word filly was first used in the 1500s and comes from the Old Norse word “fylja

Can A Filly Be A Colt?

No, a filly and a colt are not the same thing.

Though both terms refer to young horses, the term colt is used to refer to a male horse under the age of four, while a filly is a female under the age of four.

Can A Filly Be A Foal?

Yes. The term foal is used to refer to horses when they are born.

A female foal is called a filly foal from the day it’s born until it reaches the age of 12 months. After this 12-month mark, it’s just referred to as a filly, until it reaches the age of four.

Similarly, a male foal is called a colt foal from its date of birth until it reaches its first birthday. After this first birthday, a young male horse is known as a colt, until it reaches the age of four.

A quick tip: All baby horses, whether a pony, a mini-horse, or a normal horse, is referred to as a filly foal or filly colt if it’s younger than 12 months.

White Clydesdale colt foal

Foals are under the age of 12 months and can be a filly (female) or a colt (male)

Why Do Some People Call Fillies Yearlings?

This is another term often used in the worlds of horse riding and horse racing and also refers to the age of a specific filly.

You’ll refer to a filly as a yearling, once it is one year old, and until it reaches its second birthday. So, from the age of one, until two years of age, a female horse is known as a yearling.

Once a yearling filly reaches the age of two, they’re simply called fillies.

The term male yearling or colt yearling will, therefore, refer to a male horse between the ages of one and two.

Some horse lovers often use terms such as “a two-year-old filly” or “a three-year-old filly” to reference the horse’s age.

Two Clydesdale yearling fillies at Strathorn farm

They grow up quick. Belle and Freya as Yearling Fillies

Using The Term Filly In the Horseracing World

You will have noticed that the term filly is also often used in the world of horseracing.

Interestingly though, even though people in the horseracing world agree that fillies are female horses, their cut-off age for a filly is five and not four.

After its fifth birthday, the female is then called a mare.

Horse race

What Is A Weanling?

A weanling is a young foal that has been weaned off its mother’s milk.

These young horses are now able to feed on solid foods like grain, hay and grass and drink water, and do not need their mothers’ milk and care to survive.

On average, foals are weaned at the age of 6 months.

When fully weaned, a young female horse is referred to as a weanling filly, while a male horse is called a weanling colt.

Clydesdale weanlings getting their hard feed

Our weanlings starting on their hard feed

Can A Filly Become Pregnant?

Yes. Many fillies, depending on how healthy they are, can go into heat before turning four.

Some fillies can go into heat from as young as 14 months of age while, generally, female horses often go into heat at around 18 months of age.

Therefore a filly, though not yet mature or old enough to be classified as a mare, can become pregnant if exposed to an uncastrated male. It is however advised that you do not breed with your filly as they won’t be able to deal with the physical demands of pregnancy, giving birth or producing milk.

When Can I Start Training My Filly?

Fillies can be trained from a young age.

They can be introduced to halter training, lead training, and ground manners while they are still young as this builds a solid training foundation.

Most trainers will commence with full training when their fillies are around three years old and normally introduce their horses to saddles at this age. Riders are only introduced when the horse reaches the age of four or five.

Racehorses, on the other hand, can start training as yearlings and often already compete in races at two or three years old.


Can you use a filly for horse racing?

Yes, fillies are used for horse racing. An excperpt from the British Horseracing Authority explains this in more detail below

The age and type of race a thoroughbred is eligible to race in is dependent on a number of factors, these are outlined in more detail in the Rules of Racing.  In brief, a horse bred to race on the flat may not race until the start of the flat season in the year of its second birthday, whereas horses who are bred to race over jumps can’t race, at the earliest until 1st May in the year of its third birthday. There are certain age restrictions on the type of jumps race a horse is eligible to start in therefore many horses will be older than 3yrs old when they race for the first time.

Where does the word foal come from?

The word foal is an Old English word that means small or little. The word is also related to the Dutch word vulon, which means baby or child.

Where does the word colt come from?

The word colt is an Old English word that means young horse. Colt is also, in some Bible translations, used to refer to a young camel.

What are the terms used for male horses?

Male horses are called colts until they reach the age of four, whereafter they are referred to as stallions. A stallion, when used for breeding, is known as a stud. A castrated stallion is known as a gelding.

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