Some Interesting Facts About The Horse
By Dr Ann Blackburne
Horses and ponies both belong to the family Equidae. Although generally differentiated by height there are also other differences in conformation and temperament. Ponies often exhibit thicker manes, tails and coats. They also have proportionally shorter legs, wider barrels, heavier bone, thicker necks and shorter heads with broad foreheads. In all other respects however they are very similar.
Anatomy Facts
Skeleton
The horse skeleton contains a similar number of bones to that of a human. Almost all horses and ponies have the same skeletal structure with the exception of Arabians. Most horse breeds have 18 ribs while the Arabs have 17. Most horses have 6 lumbar and 18 tail vertebrae while Arabs have 5 lumbar and 16 vertebrae in their tails.
The lower limb of the horse is anatomically similar to our hand and fingers with the bones of the fingertips or toe tips encased in the hoof. In essence, a horse walks on its tip toes. Vestigial remnants of the other ‘fingers’ or ‘toes’ form the splint bones of the horse.
The hoof is made up of keratin and is essentially a larger, thicker, stronger version of a human fingernail. Like human fingernails, hooves grow continuously averaging approximately 1cm per month.
Teeth
Horses have 12 incisor teeth (6 upper and 6 lower) adapted for biting off grass during grazing and 24 premolars and molars adapted for chewing. Some horses will develop small vestigial ‘wolf teeth’ in front of the molars. These are usually removed to stop interference with the bit while riding.
The teeth continue to erupt throughout the horse’s lifetime as the grinding surface is worn down by chewing. This causes a distinct wear pattern in the incisors which allows a rough estimate of a horse’s age to be made by inspection of his teeth.
The Digestive System
The digestive tract of an average sized horse is approximately 30m long and most of this is intestines. The average horse produces 40 litres of saliva per day.
The oesophagus is approximately 1.5m long with a well developed sphincter where it passes into the stomach. This, combined with the angle at which it enters the stomach explains why horses are unable to vomit.
Horses have a relatively small stomach for their size. The stomach of an average sized horse can only hold approximately 16 litres and works best when it contains only 8 litres.
The horse’s small intestine is around 21m longs and holds up to 50 litres of ingesta. Horses do not have a gall bladder so bile flows continuously into the small intestine. The small intestine empties into the caecum which is the first part of the large intestine. The horse’s caecum is the anatomical equivalent of our appendix, however unlike us an important part of the digestive process takes part in the horse’s caecum which can measure up to 1.2m long.
The large colon, small colon and rectum make up the rest of the large intestine. The large colon is 4m long and contains over 80 litres of ingesta. Due to the many twists and turns taken by the large colon it is a common place for impactions to occur. These are a common cause of colic in the horse. The small colon is also 4m in length.
The Respiratory System
A horse’s respiratory system has amazing capacity for moving large volumes of air. If you imagine that a horse moves an average of 5 litres of air each time they breathe and they breath an average of 10 times per minute, a horse at rest moves a total of 50 litres of air through their respiratory tract every minute. At full speed a horse has the capacity to move 20 times this amount. That is, 1000 litres of air per minute. All of this air must be moved through the nose as horses are obligate nasal breathers and are unable to breathe through their mouth.
The Horse’s Heart
An average horse has a blood volume of approximately 35 litres. The average weight of a horse’s heart is 4.5kg; however Phar Lap had a heart that weighed approximately 6.5kg. The horse’s heart beats an average of 28-45 times per minute but can reach 250 beats per minute during maximal exertion. This drops significantly 15-30 seconds after the horse stops galloping.
The Eye
Horses have the largest eye of all land mammals. By virtue of their placement on either side of the head horses have 350 degree vision, although only approximately 65 degrees is binocular with the remaining 285 degrees monocular. This means that while horses have a large area of vision they have a small binocular area where they can perceive depth. The monocular vision results in the horse seeing 2 different pictures at the same time. Horses have 2 small blind areas, 1 directly in front of them and one directly behind them.
Horse’s have good visual acuity. It is considered slightly worse than that of people but significantly better than that of cats, dogs and rats. Horses also have superior night vision compared to people but find it harder to adapt to sudden changes of light like when entering or leaving dull stables or floats.
Contrary to popular belief horses are not colour blind. They have 2 colour vision as opposed to the three colour vision that we have. Horses can see colours in the blue and green spectrum but not in the red. It is likely that red colours are seen as green like with people who are colour blind.
Studies have proven that horses are less likely to knock down a rail while jumping if the rail is painted with 2 contrasting colours compared with rails painted a single solid colour.
Hearing
Horses have hearing superior to that of humans. Each ear can rotate 180 degrees giving horses the potential for 360 degree hearing without having to move their heads.
Facts about Foals
Mares tend to foal at night with the foals being able to stand within 1 hour of birth. They can walk and trot within 2 hours of birth. The legs of a new born foal are already 80-90 percent of the length they will be when the horse is full grown.
Interesting Information
Do horses sleep lying down or standing up? Both. Horses are able to snooze while standing as they have the ability to lock their hind legs in a position to stop themselves falling over. Like people though, horses prefer to lie down for a good rest. If the horse feels safe they will usually lie down to sleep. Some horses will also snore while sleeping lying down.
Only 2 coat colour pigments exist in the horse – red and black. These pigments are diluted or modified to create the four base colours (bay, brown, black and chestnut) which are further modified to create the vast number of horse coat colours seen.
The life expectancy of a horse is generally 25-30 years although a few so live into their forties. The oldest verifiable record for a horse was “Old Billy”, a horse born in the UK in 1760, living to 62 years old before dying in 1822.
The largest horse in history was a Shire horse named “Sampson” who lived in the UK in the 19th century. He was 21.2 hands high (2.2m to the wither) and was estimated to weigh over 1.5 tonnes.
The current record holder for the smallest horse is “Thumbelina” a dwarf miniature horse who measures only 17 inches in height.
Tina 20 hands, from Tennessee, and Thumbelina 17 inches
The highest jump recorded for a horse was 2.47m, a record set by an ex-race horse in Chile in 1949. The horse cleared the jump on only his third attempt.
Horses have been cloned. In 2005 a gelding used for endurance racing was cloned in Italy so that the clone could be used for breeding. It took 200 attempts and 3 pregnancies to produce 1 foal.
Horse Myths
Horse harness brasses protect the horse’s wearing them from witches.
Changing a horse’s name is considered bad luck.
If you break a mirror you should lead a horse through the house to avert the 7 years bad luck.
