| Depending on breed, management and | | | | years and over are called mares and |
| environment, the domestic horse today | | | | males are stallions. A castrated male is |
| has a life expectancy of 25 to 30 years. | | | | a gelding. Horses, particularly colts, |
| It is uncommon, but a few horses live | | | | may sometimes be physically capable of |
| into their 40s, and, occasionally, | | | | reproduction at approximately 18 months |
| beyond. The oldest verifiable record was | | | | but in practice are rarely allowed to |
| "Old Billy," a horse that lived in the | | | | breed until a minimum age of 3 years, |
| 19th century to the age of 62. The size | | | | especially females. Horses four years |
| of horses varies by breed, but can also | | | | old are considered mature, though the |
| be influenced by nutrition. The general | | | | skeleton usually finishes developing at |
| rule for cutoff in height between what | | | | the age of six, and the precise time of |
| is considered a horse and a pony at | | | | completion of development also depends |
| maturity is 14.2 hands(h or hh) (147 cm, | | | | on the horse's size (therefore a |
| 58 inches) as measured at the withers. | | | | connection to breed exists), gender, and |
| An animal 14.2h or over is usually | | | | the quality of care provided by its |
| considered a horse and one less than | | | | owner. |
| 14.2h is a pony. | | | | Also, if the horse is larger, its bones |
| However, there are exceptions to the | | | | are larger; therefore, not only do the |
| general rule. Some smaller horse breeds | | | | bones take longer to actually form bone |
| who typically produce individual horses | | | | tissue (bones are made of cartilage in |
| both under and over 14.2h are considered | | | | earlier stages of bone formation), but |
| "horses" regardless of height. Likewise, | | | | the epiphyseal plates (plates that fuse |
| some pony breeds, such as the Pony of | | | | a bone into one piece by connecting the |
| the Americas or the Welsh cob, share | | | | bone shaft to the bone ends) are also |
| some features of horses and individual | | | | larger and take longer to convert from |
| animals may occasionally mature at over | | | | cartilage to bone as well. These plates |
| 14.2h, but are still considered ponies. | | | | convert after the other parts of the |
| The difference between a horse and pony | | | | bones do but are crucial to development. |
| is not simply a height difference, but | | | | Depending on maturity, breed and the |
| also a difference in phenotype or | | | | tasks expected, young horses are usually |
| appearance. There are noticeable | | | | put under saddle and trained to be |
| differences in conformation and | | | | ridden between the ages of two and four. |
| temperament. Ponies often exhibit | | | | Although Thoroughbred and American |
| thicker manes, tails and overall coat. | | | | Quarter Horse race horses are put on the |
| They also have proportionally shorter | | | | track at as young as two years old in |
| legs, wider barrels, heavy bone, thick | | | | some countries (notably the United |
| necks, and short heads with broad | | | | States), horses specifically bred for |
| foreheads. | | | | sports such as show jumping and dressage |
| Light horses such as Arabians, Morgans, | | | | are generally not entered into top-level |
| Quarter Horses, Paints and Thoroughbreds | | | | competition until a minimum age of four |
| usually range in height from 14.0 (142 | | | | years old, because their bones and |
| cm) to 16.0 hands (163 cm) and can weigh | | | | muscles are not solidly developed, nor |
| from 386 kg (850 lbs) to about 680 kg | | | | is their advanced training complete. |
| (1500 lbs). Heavy or draft horses such | | | | Horses are adapted to grazing, so their |
| as the Clydesdale, Belgian, Percheron, | | | | teeth continue to grow throughout life. |
| and Shire are usually at least 16.0 (163 | | | | There are 12 teeth (six upper and six |
| cm) to 18.0 hands (183 cm) high and can | | | | lower), the incisors, adapted to biting |
| weigh from about 682 kg (1500 lb) up to | | | | off the grass or other vegetation, at |
| about 900 kg (2000 lb). Ponies are less | | | | the front of the mouth, and 24 teeth, |
| than 14.2h, but can be much smaller, | | | | the premolar and molars, adapted for |
| down to the Shetland pony at around 10 | | | | chewing, at the back of the mouth. |
| hands, and the Falabella which can be | | | | Stallions and geldings have four |
| the size of a medium-sized dog. The | | | | additional teeth just behind the |
| miniature horse is as small as or | | | | incisors, a type of canine teeth that |
| smaller than either of the | | | | are called "tushes." Some horses, both |
| aforementioned ponies but are classified | | | | male and female, will also develop one |
| as very small horses rather than ponies | | | | to four very small vestigial teeth in |
| despite their size. The largest horse in | | | | front of the molars, known as "wolf" |
| history was a Shire horse named Sampson, | | | | teeth, which are generally removed |
| later renamed Mammoth, foaled in 1846 in | | | | because they can interfere with the bit. |
| Bedfordshire, England. He stood 21.2 | | | | There is an empty interdental space |
| hands high (i.e. 7 ft 2 in or 2.20 m ), | | | | between the incisors and the molars |
| and his peak weight was estimated at | | | | where the bit rests directly on the bars |
| over 3,300 lb (approx 1.5 tonnes). The | | | | (gums) of the horse's mouth when the |
| current record holder for the world's | | | | horse is bridled. |
| smallest horse is Thumbelina, a fully | | | | The incisors show a distinct wear and |
| mature miniature horse affected by | | | | growth pattern as the horse ages, as |
| dwarfism. She is 17 inches tall and | | | | well as change in the angle at which the |
| weighs 60 pounds. | | | | chewing surfaces meet, and while the |
| Horse breeding | | | | diet and veterinary care of the horse |
| Pregnancy lasts for approximately | | | | can affect the rate of tooth wear, a |
| 335-340 days and usually results in one | | | | very rough estimate of the age of a |
| foal (male: colt, female: filly). Twins | | | | horse can be made by looking at its |
| are rare. Colts are usually carried 2-7 | | | | teeth. |
| days longer than fillies. Females 4 | | | | |