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What Causes Cannon Crud?

August 01, 2021 4 min read

What Causes Cannon Crud?

Searching for a new horse is a time filled with excitement and stress. It’s difficult to find the perfect match, but you think you’ve done it! You drive out to the barn, excited to meet your new riding partner. Everything looks perfect, but then you take a look at his rear legs. There-- on the front of his cannon bone-- is a weird waxy substance that looks almost scaly. You ask his owner about it, but she brushes you off saying that it never bothered him. Is she telling the truth? Should you still buy him?

Your new horse could have cannon crud. And his owner might be right! Most horses that have cannon crud are never bothered by the skin condition, but it does take some management time on the part of the owner and the right products.

What is Cannon Crud?

Chances are there is a horse on your own farm that has this unsightly, but relatively harmless, skin condition. Cannon keratosis, also called cannon crud, is a very common skin issue that impacts a wide variety of horses. As you may have guessed from the name, cannon crud develops on the front of the rear legs of the horse, directly on top of the cannon bone. It’s characterized by patches of hair loss, scaling, flaky skin, and a greasy wax stuck to the hair. Some horses have very mild cases that may be nearly unnoticeable with minimal flaking and hair loss. Other horses aren’t as fortunate with a larger area of the cannon bone impacted and more noticeable hair loss and greasy patches. 

While it may be ugly, cannon keratosis does not seem to cause pain or discomfort to the horse and mild causes often go unnoticed or ignored. However, secondary infections can develop in the weakened area without proper management and lead to significant issues such as scratches and cellulitis. 

What Causes Cannon Crud

To understand the root cause of cannon crud, you first have to understand basic equine dermatology. All horses have sebaceous glands located in the skin that produce sebum. Sebum is a natural oil that keeps your horse's coat shiny and moisturizes the skin. In some horses, the sebaceous glands along the front of the cannon bone go a little haywire and overproduce oil. The extra oil builds up on the horse's skin, trapping dirt and bacteria. This is known as seborrhea.

To visualize how cannon crud works, imagine coating your shin in a thin layer of baby oil and then going out to work in the barn. By the time you’ve mucked two stalls or groomed a horse, the oily area would be dark brown with dirt and maybe even a little sunburnt if you spent time outside. This is the same scenario for many horses with cannon crud.


While scientists know that cannon keratosis is caused by an overproduction of oil from the sebaceous glands, they’re not certain why these glands get a little overzealous in some horses.

Horses Susceptible to Cannon Crud 

Many equestrians believe that cannon keratosis is caused by urine splashing onto the rear legs of male horses, giving the condition the nickname “stud crud.” Unfortunately, the truth isn’t so simple. Cannon keratosis impacts all ages and genders of horses, which rules out the theory that only geldings and stallions have the condition due to the way they urinate.

While scientists have been unable to link the development of cannon keratosis to a single cause, they have been able to find several different predispositions to cannon crud development in horses. Populations of “thin-skinned” horses, such as thoroughbreds and Arabians, tend to have higher proportions of cannon keratosis. According to Dr. David Wilson, “Systemic diseases such as intestinal malabsorption, liver disease, mineral and vitamin deficiencies or imbalances, toxicosis, neoplasia, or endocrine diseases can predispose horses to develop secondary seborrhea.”

If you notice cannon crud on your horse, it could be a secondary development from a larger issue, such as a mineral or vitamin deficiency. Talk to your vet about having your horse checked for an underlying issue. 

Cannon Crud is Easily Mistaken For…

A lot of equine skin conditions cause hair loss and scaling so it’s easy for cannon keratosis to be mistaken for another condition or vice versa. Skin issues like equine dermatitis, urine scald, and photosensitivity can lead to much more serious issues involving pruritus and bacterial infection. If you notice hair loss, greasy skin, scaling, or flaking on your horse’s rear legs, don’t assume it’s cannon crud. Because these other “look-alike” conditions require more intense management before they lead to issues like lameness, have a chat with your veterinarian so you know exactly what you’re dealing with. 

How to Manage Cannon Crud

The truth is there is no foolproof management protocol when it comes to cannon crud. Because many horses are genetically predisposed to the issue, the prognosis  for complete resolution is poor. However, just because the chances of curing cannon crud are slim to none, doesn’t mean that with proper management you and your horse can’t live a normal life and achieve your riding dreams. Most of the time, cannon keratosis has no impact on quality of life for the horse and with proper management, the condition can be minimized. 

Start by checking the area daily for signs of worsening. Watch for signs of secondary infection, such as increased inflammation, reddening, and oozing. Gentle grooming can help loosen the waxy patches and bring more blood flow to the cannon bone. But whatever you do, don’t pick, scrub, or aggressively groom the area. Aggressive grooming can actually worsen cannon keratosis and cause secondary infection by creating minute abrasions on the surface and weakening the skin.

Support your horse’s skin health and strengthen the dermal barrier by using a topical equine barrier cream. Zarasyl’s non-toxic and non-irritating formula is perfect for gentle support of the skin without irritating the keratosis. Zarasyl contains a proprietary amorphous silica with a molecular structure tailored to provide sustained delivery of orthosilicic acid to the skin. Orthosilicic acid is the bioavailable form of silicon associated with healthy connective tissue growth. 

Try Zarasyl today. Buy your tube here.