Are any horses naturally tailless?

Rarely. There is one Austrian Thoroughbred stallion, Shellscrape, who was retired from stud duty after 20 percent of his foals were born with shortened, crooked, or missing tails.

However, there is no "bobtail" gene in horses (or draft breeders would have made use of it to produce naturally short tails). A lack of a tail or a shortened tail is symptomatic of a spinal deformity (or it means the tail was cut off either for "tradition" or because it was damaged and had to be amputated). It can be a symptom of spina bifida.

A docked Clydesdale (image source Kersti Nebelsiek via Wikimedia Commons).

Appaloosa horses often have short tails, but the actual tail (the dock) is full length - they just don't grow much in the way of hair on it.

Donkeys are more commonly born with a short or missing tail, and its possible there is a bobtail gene in donkeys, but it has never been bred for if so.

What is a daisy cutter?

A daisy cutter is a horse that moves without lifting its feet much off the ground - it's considered a desirable trait in stock horses because it allows for a much more efficient stride at speed. Some Thoroughbreds also "daisy cut."

It can be a problem when the horse is asked to move through deep going, however.

What is the jugular groove?

If you look at a horse's neck, you will see a groove towards the bottom on both sides. This is the jugular groove, and it contains the jugular vein and carotid artery (making them rather vulnerable - this is where a predator is likely to go for).

Because of the way this horse is standing, the jugular groove is extremely visible.

What is the gaskin?

The gaskin is a big muscle found on the horse's hind leg above the hock. It's analogous to our calf (remember, horses stand on tippy toe).

This very fit Appaloosa mare has a powerful gaskin - you can see how the leg bulges a little on the outside.

What is the chin groove?

If you look at a horse's face, you'll see they have a dip on the lower jaw, about where the corner of the mouth is. We call that the "chin groove."

You can see it here on this Icelandic horse, right before where her chin gets all shaggy.

What is "flat bone?"

Flat bone is an old term for a horse with "flat" legs. Obviously, the bone itself is not flat, but a well-conformed lower leg with round bones and tendons and ligaments in the right place appears flat from the side - this is considered highly desirable for soundness.

What is a "shark fin?"

A horse with a "shark fin" has unusually high withers. They are most often seen on Thoroughbreds, and there may be some connection between high withers and speed - it may help the horse reach further forward with each stride. Shark fins can cause major problems with saddle fit (and trust me, never get on a horse with one bareback). Just as an obese horse may appear mutton withered, an underweight or very out of shape horse can appear to have higher withers (horses build muscle above their spine as a result of carrying the rider's weight).

The gelding in the foreground is slightly underweight (he's a rescue and very old) and at least appears to have shark fin withers.

What are "mutton withers"?

Mutton withers are flat and wide. This can cause problems with saddle fit - the saddle tends to slip sideways or forward. It's most commonly seen in ponies. Also, an obese horse may appear to be mutton withered.

Note the almost complete lack of a bump in front of the saddle area on this Icelandic mare.

What is a "pigeon-breasted" horse?

A pigeon-breasted horse appears to have a "wishbone." It's actually caused by the front legs being set a little too far back. It can affect a horse's gait, but can actually help the horse make quick turns.

(You have to look carefully to see it because it's behind this Paint horse's head, but he is definitely pigeon-breasted).

What is "slab sided"?

A slab sided horse is one that has straight sides, with the ribs flat and aligned vertically. It's considered a flaw because it limits the space available for the lungs to expand.

What is a bull neck?

A bull neck is an excessively short and thick neck - one that resembles the neck of a cow. It's actually considered desirable in pulling horses (the collar sits better), but undesirable in riding horses as the horse finds it harder to balance.

This rather scruffy Mongolian horse has a bull neck - and a very pretty saddle. Image source: Latebird via Wikimedia Commons.

What is a dished face?

A dished face is a concave profile of the horse's head, sometimes with a bulged forehead. Extreme dishing is most often seen in Arabians, but many pony breeds also have slightly dished faces. In Arabians, the dish is desirable and associated with stamina - it's assumed that it has something to do with having the right airway for endurance work in warmer climates. (Pony dishes are much less extreme).

This Arabian only has a slight dish, but the forehead bulge is visible. Image source Ealdgyth via Wikimedia commons.

What is "pig eyed"?

A pig eyed horse is one that has disproportionately small eyes. It is generally considered a fault, both because it's viewed as unattractive and because it's associated with stubbornness or anxiety. This latter may have some truth to it - the smaller eye may result in less peripheral vision. For the most part, though, it's an aesthetic problem.

This chestnut horse has a pig eye, and the eyelid does not appear to open all of the way. Image source: Rachael C via Flickr.

How many vertebrae does a horse have?

Horses have pretty long backs - so, you would think they have a lot of vertebrae. Actually, a normal horse has 18 thoracic vertebrae (the ones with ribs attached), five of which form the withers, and six lumbar vertebrae. Arabians often have only 17 thoracic and five lumbar vertebrae.

Humans, in contrast, have 12 thoracic and five lumbar. This is not counting the neck, of course. Of course, this means that horse vertebrae are quite a bit larger than ours.

What is camped under?

A camped under horse stands with his front leg behind the vertical. It's considered a fault mostly because such horses tend to be more likely to trip in front (which can be dangerous for the rider).

What is camped out?

Camped out is when the horse stands with its forelegs set too far forward, the hoof in front of the shoulder. In some horses this is a conformation fault. However, a horse that is in pain or footsore in the front legs may also stand camped out - it's common with horses suffering from laminitis.

What are sickle hocks?

Sickle hocks are hocks with too "tight" an angle, with the cannon bone being too far underneath the horse. This puts extra strain on the ligaments at the back of the leg, although some reiners like it as it allows the horse to "sit" better when doing spins and sliding stops.

What is a swan neck?

A swan neck is a neck that curves correctly at the top, then dips at the bottom. It often appears to have an excessive arch. A horse with a swan neck finds it easier to lean on the bit or evade it by ducking behind it, so it's not desirable. It often happens when breeding for a more arched neck.

What is a ewe neck?

A ewe neck, sometimes called an "upside down" neck is a neck that dips in front of the withers, causing a high head carriage and hollow back. An upside down neck can either be a conformation fault or caused by poor riding and training leading to incorrect muscle development - or some combination of the two.

What are fox ears?

Fox ears on a horse are ears which point slightly inward at the top rather than being straight. They have no effect on a horse's hearing or usability, but some people like them.