When it comes to horses, there are different terms used to describe their age and gender. One such term is “filly.” In this article, we will explore what makes a horse a filly and the distinction between a mare and a filly.
Definition of a Filly
A filly is a female horse that is too young to be called a mare. It refers to the gender and age of the horse. In most cases, a filly is a female horse under four years old. However, the specific definition can vary across different nations and disciplines. For example, in the world of horse racing in the United Kingdom and the United States, the cutoff age for fillies is typically set at five years old.

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Difference Between a Mare and a Filly
The main difference between a mare and a filly is their age. A mare is an adult female horse or equine. In most cases, a mare is a female horse over the age of three. On the other hand, a filly is a female horse three years old and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four years old.
It is worth noting that the term “filly” is often used in the context of horse racing and breeding. Once a female horse reaches the age of four, it is generally considered a mare. However, the cutoff age may vary depending on the specific discipline or country.
Identifying a Filly or a Colt
It can sometimes be challenging to determine if a foal is a filly or a colt. A foal refers to a baby horse, and the terms filly and colt are used to differentiate their gender.
The best way to identify the gender of a foal is by observing its external genitalia. However, it is recommended to seek assistance from a veterinarian or an experienced horse professional to make an accurate determination.
Age and Transition to a Mare
A female horse under the age of four is called a filly. Once a filly reaches the age of four, it is considered a mare. The transition from filly to mare is mainly based on age and maturity. It is essential to monitor a horse’s development and assess when they reach the appropriate age to be classified as a mare.
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Frequently Asked Questions On What Makes A Horse A Filly
What’s The Difference Between A Mare And A Filly?
A mare is an adult female horse or equine over the age of three, while a filly is a female horse three years old and younger. In Thoroughbred horse racing, a mare is defined as a female horse over four years old.
How Do You Tell If It’s A Filly Or Colt?
A filly is a female horse under four years old, while a colt is a male horse under four years old.
At What Age Is A Horse No Longer A Filly?
A horse is no longer a filly once it reaches the age of four. At that point, a female horse progresses in classification from a filly to a mare.
At What Point Does A Filly Become A Mare?
A filly becomes a mare at four years old. A female horse under four years is considered a filly; over four years, she’s a mare.
Conclusion
In summary, a filly is a young female horse that is too young to be called a mare. The specific age cut-off can vary depending on the country and discipline, but in most cases, a filly is under the age of four. Understanding the distinction between a mare and a filly is crucial for horse enthusiasts, especially in the context of horse racing and breeding. It is recommended to consult with experts in the field to accurately identify a horse’s gender and age.