What is a baby horse? This is one of those great questions that flies around a lot because it’s so often confused! Here’s the true and definitive rundown of the main horse designations
- A baby horse of any gender from birth until it is one year old (or with some breeds like the Thoroughbred, until midnight on December 1 of it’s birth year, regardless of the actual birth date) is called a foal.
- A filly is a female horse under the age of 4. (In racing, the age cutoff for the filly designation can be 5 years old.) After which they are designated as a mare. The mare status is not upon reaching estrus as often believed. (generally the rule reflects the time when the filly stops growing)
- The male version of this is a colt. ("Colt" and "foal" are very commonly used interchangably, which despite being common, is actually incorrect)
- A foal of any gender between the time it is weaned until it becomes a Yearling is called a Weanling. (They may be referred to as a weanling filly or weanling colt)
- Foals become Yearlings when they reach their first birthday (or on January 1 in the case of Thoroughbreds and other breeds with this rule). Following that they are referred to as 2 Year Old Colt/Filly, 3 Year Old Colt/Filly and so-on. (Or simply just 2 Year Old, 3 Year Old and so on.) Again, this terminology is founded in Throughbreds so to designate racing class and eligibility, but it is the accepted norm across breeds.
- A male horse that is castrated is called a gelding.
- An uncastrated horse that has reached breeding age is called a stallion.
- An uncastrated horse that is specifically being used as a breeding horse, or “standing at stud” may also be called a stud. Stud and stallion are often used interchangably - generally the designation seems to be delineated by discipline, though most breeds refer to recognized male breeding horses as stallions.