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