Laminitis is probably by far the most devastating disease that a horse and horse owner will ever face. The definition of laminitis is nothing more than inflammation of the lamina or the tissue of the foot, but that does not describe the devastating pain and struggle that a horse faces with this disease. There are many sources of laminitis or foundering in horses. I will cover some of the most common causes, ways to avoid these causes and treatments.
The foot is an amazing organ for the horse and it is amazingly resilient but at the same time very fragile. The equid foot has to endure nearly constant loads of just daily locomotion but also endure very high levels of load during events such as racing, jumping and pulling. The tissue that holds the foot attached to the coffin bone is only a few millimeters thick but is amazingly strong. The tissue looks like Velcro under a microscope and is very rigid but also at the same time allows the foot to flex, grow and expand. The metabolic energy and blood flow rate that feet require to with stand this load is incredibly high as well. The blood flow to the very farthest part of the horse is complex and important when addressing laminitis which will be discussed later.
- Grain overload or carbohydrate overload
Consumption of a large amount of grain can lead to gastrointestinal disruption leading to founder. A horse that breaks into the feed shed and consumes large amounts is the most common scenario that is seen. These horses need to have as much grain removed from their stomach as soon as possible with a stomach tube and then products such as activated charcoal administered to help bind toxins that may be produced from bacteria dying off from the high grain load in the gut.
- Metabolic conditions – PPID (Cushings) and EMS (Equine Metabolic Syndrome)
Horses with cushings have high levels of glucocorticoids circulating in their blood leading to disruptions of the lamina along with other body systems. These abnormally high glucocorticoids are caused by an abnormality with the pituitary gland in the brain. This can be corrected when diagnosed with medication.
The EMS horses have high levels of insulin which has been found experimentally to induce laminitis. Horses that are obese and get very little exercise are at risk of EMS. EMS is reversible and prevented by managing diet more closely, routine exercise and preventing access to lush green pastures.
- Lush green grass (Grass Founder) – commonly seen in overweight EMS horses
Similarly, horses with underling EMS can found on lush green growing grass because of the high sugar content in these grasses. In the spring with good grains and plenty of sunshine grass can grow rapidly. This rapid growth phase of grass produces larger amounts of sugars in the blades of the grass during photosynthesis. It has been discovered that during peak sunlight is when the highest sugar content is found in the grass because of higher amounts of photosynthesis occurring in the grass blades.
- Endotoxemia – Caused by severe illness such as sepsis, colic, pneumonia
Horses that have serious bacterial infections or acute colitis can absorb endotoxins released by the dead bacteria. Horses are extremely sensitive to endotoxins and these toxins are called LPS (lipopolysaccharides) that make up part of the bacteria cell wall. When a large amount bacteria are killed off with antibiotics or disruptions in the horses gut these toxins are absorbed causing lots of problems for the horse.
- Overloading weight – injuries that cause the horse to bear more weight on another limb
Overbearing weight on other limbs from an injury to another limb can cause contralateral limb laminitis. Just by shear overloading force breaks down another foot. This can occur when a major injury occurs to a limb forcing more weight onto another because of pain. This is seen commonly with fractures, serious soft tissue injuries and neurologic conditions. This is what led to the death of Barbaro, the famous thoroughbred race horse that fractured his leg during the Preakness.
- Black Walnut – Shavings containing black walnut can induce laminitis
The species of tree can be very toxic to horses and must never be used as bedding or shavings that will come in contact with horses. It has been estimated that shavings containing as little as 5% black walnut can be toxin to horses. Some research has even thought that contact along can be deadly.
Diagnosing laminitis is rather straight forward. Examination of the horses gait at a walk or trot will indicate lameness. Most horses in acute founder will be severely lame at a walk and will be shifting weight back to the hind limbs in order to move or change directions when ask to ambulate. Horses will have an increased pulse in the arteries near the feet called a digital pulse. This pulsation of blood is similar to the throbbing sensation that we feel have an acute injury to a finger or limb and is quit notable in acute laminitis. Heat can also be noted around the coronary bands and hoof wall.
Radiographs or x-rays are used determine the severity of laminitis by measuring the separation of the coffin bone from the hoof wall. Venograms are also used to identify the blood flow damage to the foot using contrast dies injected into the digital veins while a tourniquet is applied above the foot. The contrast highlights the blood vessels so they can be seen with x-ray.
Treatment of Laminitis
First of the underlying cause of the laminitis must be eliminated or managed in order to get the laminitis under control or the battle will be very difficult. For example if a horse with EMS is not put on a serious diet and their weight managed you will be fighting a losing battle. Secondly a veterinarian and a farrier team are going to be needed to help manage the horse’s feet to prevent further laminar damage and provide the best possible foot support needed. Veterinarians must provide pain management, systemic care or treatment of the underlying illness and administer other medications that can benefit the horse in order to eliminate laminitis. Farrier’s have the daunting task of providing support of 1,000 pound or more horse that has feet sometimes the size of tea cups. The goal for farriers is to provide the proper support with various different methods across the sole of the foot at the same time eliminating stress and forces that inherently designed into the horse’s foot. Care for the horse’s feet is very critical and requires a skilled team to provide the best care. Lastly is that you have to be in it to win it. Short cuts and half hearted attempts are usually not very fruitful when it comes to dealing with laminitis. Below is a list of treatments used to treat laminitis.
- Medication or surgery to correct the underlying cause
- Cryotherapy or icing of the lower limbs and feet
- Systemic anti-inflammatory drugs and pain management
- General health care such as a good diet, deep beading, management of other illnesses and supportive care
- Corrective foot care
- Surgical intervention with tenotomies (cutting the deep digital flexor tendon)
- Slings (rarely available and only in extreme cases)
Laminitis or founder can be very challenging to correct or manage. It is not uncommon to humanely euthanize horses for acute or chronic causes of founder. These horses are often losing weight, unable to get up and ambulate well enough to eat or drink frequently enough. Often it is important to have a discussion of quality of life on behalf of the horse and do what is necessary so the horse is not suffering. These are always difficult decisions but they are necessary and always good to have these with your veterinarian and farrier that are caring for the horse.
Read more about your horse’s health in the latest issue of Oklahoma Farm & Ranch magazine.
Equine Flexural Limb Deformities
By Dr. Garrett Metcalf
Flexural limb issues can occur in different age groups of horses, starting with newborns up to two- to three-year-olds. These issues occur somewhat predictably in age groups and can be addressed rather quickly when needed. There are various treatments and methods that can be used to address flexural issues. This article will discuss the most common flexural abnormalities and treatment methods.
Foal Flexural Issues
Foal flexural issues are often considered congenital flexural limb abnormalities because they are born with them. We don’t fully understand why this occurs but there is some evidence in the human literature that lack of fetal activity in the womb causes club feet in babies. In foals, it is thought that uterine positioning is to blame for part of the contracted tendons. Other causes can be exposure of the mare to toxic plants or substances that may be toxic to the fetus.
The most common area that a foal will have contracture of limb is at the carpus or knee. These foals will not be able to fully extend the knee and often will affect both at the same time. These foals can have difficulty standing to nurse or will get fatigued quickly and will not be able to stand for longer periods of time. There can also be damage to the extensor tendons or even rupture of extensor tendons caused by the high strain placed on them when the foal tries to stay standing. The rupturing of these tendons is not overly concerning but the lack of extensor function can make the flexural limb deformity worsen.
Other common locations of flexural limb deformities can be at the fetlock or coffin joint level. These deformities are not usually as detrimental to allowing the foal to stand and nurse properly compared to carpal flexural deformities. These deformities can be addressed similar to carpal deformities with some exceptions.
Treatment of Flexural Deformities
Splints or casts can be used to stretch and support the effected limbs of foals. Splints are often preferred by most veterinarians because they can be repositioned or reset as needed. Splints are easier to place on the limbs of foals but they do need resetting every 24 to 48 hours. Casting of the limbs is more rigid but is not adjustable once placed. Casting is often needed in more severe cases and requires changing frequently. Whenever placing these devices, care must be taken to prevent splint or cast sores because foal skin is rather delicate.
Surgical intervention is needed in some cases of carpal flexural deformities. A study out of Australia found that cutting of two muscle/tendon groups on the back of the carpus greatly improved the ability to extend the carpus with splinting methods. Cutting of these tendons do not have consequence to future athletic function. The two muscles are called flexor carpi ulnaris and ulnaris lateralis.
An antibiotic called Oxytetracycline is helpful to treat flexural limb deformities because of its side effect of causing tendon laxity. The laxity is created by chelating calcium within the tendons and allows the relaxation of tendons. This method does have some risk because of the high dose required and renal injury that it can cause when not administered with IV fluids.
Toe extension shoes are used when it comes to dealing with lower limb flexural limb deformities. These shoes are often applied with adhesives and after the splinting or casting is no longer needed. The toe extension shoe allow foal to continue to stretch those tendons every time they take a step and prevent from becoming contracted again.
Older horses (six months or older) with contracted tendons often get acquired limb deformities and the horses need surgical intervention to correct these deformities. These surgeries cut or release check ligaments that allows the musculotendinous unit of the deep digital or superficial digital flexor tendon to elongate. The deep digital flexor tendon is responsible for causing club feet or a flexural limb deformity at the coffin joint. The superficial digital flexor tendon is responsible flexor tendon that causes a flexural limb deformity at the fetlock joint. The check ligaments attach the tendon to bone and do not allow the tendon to elongate past a certain point. By eliminating these ligaments the flexural limb deformity can be corrected by allowing the muscle to stretch since the tendon is much more rigid.
Flexural limb deformities can be caused by excessive laxity or weakness of the tendons. These deformities are often seen in premature foals or foals that are born at a much smaller birth weight. The excessive laxity will cause the toes of there feet to flip up in the air and the fetlocks to be touching the ground. The areas where the skin is contacting the ground will cause sores and abrasions. If these areas are note protected the wounds can get into deep structures causing serious infection and injury the flexor tendons.
Treatment for tendon laxity is to add heel extension shoes to keep the toes flat to the ground. The extension behind the foot forces the toe down under the foals own weight. As the foal becomes stronger from normal activity the muscle attached to the tendons can support the foal and the limb laxity will correct itself. Abrasions still can occur even with heel extension shoes are in place so bandages need to be applied to protect these areas.
Flexural limb issues are a common issue that horses and owners will face. It is best to have your horse evaluated by a veterinarian whenever these problems are suspected. Foal flexural limb deformities can be life threatening because of the limitation of standing on time to nurse colostrum. Without colostrum within the first hours of life the foal is a much higher risk of sepsis and death.
Read more in the August 2023 issue of Oklahoma Farm & Ranch.
Equine Foot Abcesses
What a pain!
By Dr. Garrett Metcalf, DVM
A foot abscess is a common occurrence in horses throughout the year. Often wet weather can play a factor in the increase number of foot abscesses that horses will experience. A foot abscess can cause a great deal of pain, lameness, swelling and misery to the horse that often needs to be addressed quickly and provide pain management to keep them comfortable. There are many methods of addressing a foot abscess that people use. This article will discuss techniques to evaluate and treat the abscess as quickly as possible.
Foot abscess is a focal or sometimes diffuse infection that is trapped between the sensitive and non-sensitive lamina of the foot capsule. A foot abscess can form randomly from the normal stresses and environmental changes that cause the foot to allow bacteria to enter down to the sensitive tissues. Other causes are penetrating injuries to the bottom of the foot that allows bacteria to enter the through the outer lamina, such as nails, sharp rocks or even thorns. Poor foot care and misplaced shoeing nails can also lead to foot abscesses. A common area for abscesses to form is at the white line (area where the sole and hoof wall meet) and at the bars of the heels.
Foot abscess can cause a horse to have variable amounts of lameness, but generally they will be lame at a walk or even be non-weight bearing from the severity of the pain. Swelling starting at the foot and working its way up the limb can be noted when the abscess is trying to migrate out at the coronary band. These types of abscess are often referred to as “gravel” abscesses. “Gravel” is no more than just a regular foot abscess that has found the path of least resistance to the coronary band, where it ruptures out and causes a draining tract. An abscess in the hind foot can make the horse move rather abnormal to the point that it makes owners and veterinaries perceive the horse as acting neurologic.
Examination of the horse for lameness is the first step in diagnosing a foot abscess. The horse will often be lame at walk but some need to be watched at a trot to determine the lame limb. Lameness localization with regional nerve blocks can help make sure the pain is coming from the foot and not other parts of the limb. The foot will often have an increase digital pulse with occasional notable heat in the foot. The pulse is from inflammation causing a bounding of the digital arteries most notably behind the ankle region. The foot examination often needs to be performed with the shoe removed from the foot if the horse is shod. Hoof testers help pinpoint the area of most concern on the foot and often horses will be rather painful in response to the pressure created by the hoof testers. Knifing the foot out to clean up and remove any old sole or frog material is imperative to be able to locate the abscess with as much accuracy as possible. Often there will be a defect in the hoof or a dark focal tract that will lead to the abscess.
Treatment of the foot abscess can be done multiple ways and many people have lots of opinions on this topic. My treatment of choice is to open that abscess as soon as possible to give the horse nearly immediate relief and to quickly resolve the abscess infection. There are many methods to doing this but a good sharp hoof knife or loop knife one of the easiest ways to get the abscess drainage through the bottom of the foot. Whenever drainage of the abscess is achieved at the bottom this can eliminate the formation of a “gravel” and keep it from migrating out at the coronary band. Also drainage at the bottom allows a more effective treatment of the abscess with topically applied poultice agents. After the abscess has been opened to drain, bandaging the foot with a poultice agent is effective at eliminate the abscess and preventing foreign material from packing to the abscess area.
A great method of bandaging the foot is with the use of a large baby diaper. The diaper is very absorbent and foots the foot rather well. The diaper can be covered with layers of Vetrap, Duck Tape and Elaskiton to keep it protected or the foot can be placed in a medicine boot to keep the diaper protected.
Poultice choices are rather personal experience or availability, but also depend on the nature of the abscess. Epsom salt based foot poultice agent called Magna Paste or similar products are rather good at drawing out the remaining part of the abscess once it is opened. A homemade poultice of sugar combined with Betadine solution can make a really good poultice. There are various other topical agents that can be used effectively. The main thing when choosing a topical product is to make sure it is safe and that it has some antimicrobial properties.
Some foot abscess cases can be difficult to pinpoint and to drain. In these situations often time, pain management and soaking of the foot in Epsom salt water baths can help to allow the abscess rupture or make it easier to identify. In rather difficult abscess or when abscesses keep reoccurring in the same location, X-ray imaging of the foot is helpful to examine the structures of the foot. The abscess itself cannot be seen often with X-ray because the abscess fluid is the same density as the hoof wall. The only way to identify an abscess on X-ray is if there is gas present in the abscess making it visible on the film. Whenever there is a penetrating injury to the foot, X-ray is a must to make sure that the injury is not going into the deeper structures of the foot like the coffin joint or navicular bursa. These injuries are much more serious and need to be examined as quickly as possible. It is also recommended whenever possible to leave the penetrating object in the foot until the X-ray is taken. This will help the veterinarian understand what structures may have been injured.
Prevention of foot abscess is not always possible but a great start to this is really good hoof care. Routine trimming on a timely schedule is key part of good hoof care. The longer the feet go without a trim can affect the lamina and cause stretching of the white line, opening it up to allow bacteria to enter the foot. The use of special shoeing nails and other methods of good shoeing practices also limit the risk of abscessation.
Read more in the June issue of Oklahoma Farm & Ranch.
Guttural Pouch Diseases of Horses
The guttural pouches of horses may not be very well known to most horse owners. These bilaterally paired pouches are located below the base of the skull, below the ears and extend into the throat latch region. The pouches purpose is not fully understood, but some theories is that they reduce the weight of the skull or have a blood cooling function to reduce the temperature of the arterial blood going to the brain. The guttural pouches can be plagued with a multitude of issues that are difficult to treat or can be life threatening to the horse. Other species contain guttural pouches such as some bats, American Forest mouse and Hyraxe.
The anatomy of the guttural pouches is complex and houses various important anatomic structures. The guttural pouches are an auditory tube diverticulum that is analogous to human Eustachian tubes but much larger. The volume of the guttural pouches can be up to 400-600 milliliters of air. The guttural pouches contain large arteries, nerves, the bones of the inner ear, muscle tissue and part of the hyoid apparatus that connects the skull to the larynx. The opening of the guttural pouches is deep in the nasopharynx through the slights call the pharyngeal ostium, which can only be accessed with an endoscope passed up the nose. The difficulty of accessing this area makes treatment of these diseases challenging at best. The guttural pouch is the only location in the horse that allows direct visualization of the arteries and nerves. The main arteries that are present in the guttural pouch are the maxillary artery and the internal and external carotid arteries that provide all the blood to the skull. The nerves in the guttural pouch are cranial nerves that exit directly from the brain or brain stem that innervate critical structures that control breathing, swallowing, chewing and ocular functions of the skull.
Read more in the April issue of Oklahoma Farm & Ranch.
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