The age and sex of a racehorse are two important characteristics which can influence a horse’s racing career.
In the northern hemisphere all thoroughbred horses have their official birthday on 1 January, regardless of when they were actually born. So a horse born in November will actually turn one year old (a ‘yearling’) just two months later in January.
This universal birthday can have racing implications. Flat racehorses start their racing career at two years old and the universal birthday means there can be some ‘old’ and ‘young’ two-year-olds taking to the racecourse.
In theory the youngest ‘two-year-old’ could actually have only been alive for one year.
E.g. born 31 December 2012; turn one year old on 1 January 2013 (one day after it was born); turn two years old on 1 January 2014 (when the horse has only been alive for 12 months).
At the other extreme a foal born on 2 January will actually be a year old when it has its official birthday the following 1 January.
So the ideal is to have a foal born in the early months of the year because it will be more mature and physically developed when it takes to the racecourse. Over time any difference in physical maturity and development diminishes.
In the southern hemisphere the official birthday is 1 August.
Yearling: a one-year-old horse i.e. in the second year of its life
Juvenile: a two-year-old racehorse
Colt: a male horse up to and including the age of four-years-old
Filly: a female horse up to and including the age of four-years-old
Horse: a male horse aged five or older
Mare: a female horse aged five or older
Entire: an ungelded (not castrated) male horse, also called a ‘full’ horse
Gelding: a male horse that has been castrated
Stallion: a male horse used for breeding purposes
Broodmare: a female horse used for breeding purposes
The age and sex of a horse can determine the races in which it can participate as some races are open only to certain age groups or sexes. For example:
• The 1,000 Guineas race is open to three-year-old fillies only
• The 2,000 Guineas is open to three-year-old colts and fillies
• Geldings are not allowed to take part in the Classic races: 2,000 Guineas, 1,000 Guineas, Derby, Oaks, St Leger
• A nursery race is a handicap race for two-year-olds
• In jumps racing veterans races are open to horses and mares aged 10 or older
• There are also mares only races
