filly

{{Short description|Young female horse}}

{{About|the type of horse|the American city|Philly}}

A filly is a female horse that is too young to be called a mare. There are two specific definitions in use:

• In most cases, a filly is a female horse under four years old.
• In some nations, such as the United Kingdom and the United States, the world of horse racing sets the cutoff age for fillies as five.{{cite book |last=Hammond |first=Gerald |title=The Language of Horse Racing |url=https://books.google.com/books?id=CJ4zH2P_6mMC&q=colt|year=2000 |publisher=Taylor & Francis |location=London |isbn=1-57958-276-1 |oclc=44923115|page=79}}{{cite news|url=http://www.breederscup.com/content.aspx?id=36192 |title=Zenyatta completes perfect season |first=Jay |last=Privman |work=Daily Racing Form |publisher=Breeders' Cup |date=October 24, 2008 |access-date=September 7, 2011 |quote=It was the perfect end to a perfect day by a perfect filly. Zenyatta, the best older female horse in the country, completed a perfect season. . . by winning the $2 million Ladies' Classic on Friday at Santa Anita's Oak Tree meeting, the first of two days of the 25th Breeders' Cup championships.}} (Zenyatta was foaled in 2004, making her a 4-year-old at the time.)

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| header = Fillies of different ages

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| image1 = Rock's-anne-supreme-winner.jpg

| alt1 = A weanling filly

| caption1 = A weanling Warmblood filly

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| image2 = Kate (Major AA x Bey Sharose).jpg

| alt2 = A yearling filly

| caption2 = A yearling Arabian filly

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| image3 = Major-Emblem IMG 1211r2 20151213.JPG

| alt3 = A two-year-old filly

| caption3 = A two-year-old Thoroughbred filly

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| height4= 500

| image4=Alegra (5850263824).jpg

| alt4 = A three-year-old Arabian filly

|caption4=A three-year-old Arabian filly

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Fillies are sexually mature by two and are sometimes bred at that age, but generally, they should not be bred until they themselves have stopped growing, usually by four or five.Ensminger, M. E. Horses and Horsemanship: Animal Agriculture Series. Sixth Edition. Interstate Publishers, 1990. {{ISBN|0-8134-2883-1}} p. 149-150 Some fillies may exhibit estrus as yearlings.

The equivalent term for a male is a colt. When horses of either sex are less than one year, they are referred to as foals.{{Cite book|title=Modern Livestock and Poultry Production |author=James R Gillespie|year=2000|publisher=Thomson Delmar Learning|url= https://books.google.com/books?id=_yVilNaM4z0C&q=Filly+definition+horse&pg=PA645|isbn=978-0-7668-1607-7}} Horses of either sex between one and two years old may be called yearlings.