June 2019 - Lower Respiratory Diseases in the Horse
Respiratory conditions in the horse are never anything to sneeze about, especially when it comes to equine influenza, herpesvirus, asthma or even "heaves." Pose your questions for this month's expert, Dr. Lynn Martin, related to respiratory diseases in the horse.
Click here to read this month's questions and answers.
- What are your thoughts on barefoot trimming for horses with moderate navicular disease? (View Answer)
Navicular disease is a syndrome affecting not just the navicular bone itself, but the entire podotrochlear apparatus located in the heel of the foot. Advanced imaging modalities, such as MRI, have allowed us to determine the specific structures that are injured when a horse is experiencing heel pain. The more specific the diagnosis, the better your veterinarian can direct their treatment and shoeing recommendations.
In general, there are two things we would like to accomplish when shoeing a horse with heel pain. These principles include reducing extension of the coffin joint, and decreasing the peak pressure on the navicular bone by unloading the deep digital flexor tendon (DDFT). With farriery you are able to provide pain relief by applying both static and dynamic shoeing principles. An example of a static shoeing principle for heel pain would be the use of a wedge pad to raise the heel and unload the DDFT. In this scenario, a wedge pad changes the biomechanics of the foot at all times, even while at rest. With navicular disease, permanent heel elevation can sometimes be detrimental as it can induce contraction of the DDFT. Barefoot trimming would require you to implement similar static shoeing principles, with the goal of heel elevation and improving breakover at the toe and quarters.
Therapeutic farriery also emphasizes the use of shoeing principles that have a dynamic effect. In the case of dynamic shoeing, the biomechanical effect only occurs in deformable footing. At rest, the biomechanics of the foot are unchanged. An example of a dynamic shoeing principle for heel pain would be the use of a flat reverse shoe. A reverse shoe prevents the heel from sinking while the horse is being worked, unloading the DDFT. The absence of a bar at the toe also encourages the toe to sink and allows the horse to wear its toe, maintaining ease of breakover throughout its shoeing cycle.
Both static and dynamic shoeing principles have their place in certain scenarios and for specific injuries. In the case of navicular disease, barefoot trimming requires you to apply static shoeing principles and may not be as beneficial as utilizing a dynamic therapeutic shoeing principle for the management of heel pain. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- What does a normal hoof look like? (View Answer)
The following AQHA interview with Dr. Stephen O'Grady provides a nice overview of the normal structure of a healthy equine hoof.
Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- As I watch my horse walk towards me, I can see that the outside of her left front foot lands first then the inside. She also has a lot of arthritis in her left fetlock area. Can my farrier do anything to make her front feet more balanced? (View Answer)
Uneven hoof placement does not necessarily mean that your horse’s feet are unbalanced. Foot fall can also be significantly affected by conformation. The two main means for evaluating medial-to-lateral (inside-to-outside) hoof imbalance include hoof measurements and radiographic evaluation. Radiographs (x-rays) are beneficial because they can make subtle imbalances more obvious and identify other abnormalities that may also require correction, such as a negative palmar angle. A radiographic shoeing consultation will allow your veterinarian and farrier to collaborate on what is best for your horse’s specific ailment.
Abnormal foot fall, regardless of the cause, can result in asymmetric joint loading. Abnormal joint loading has been implicated in the progression of osteoarthritis. Your farrier could apply a shoe with a heavily beveled medial (inside) quarter and branch to aid in medial breakover. This will reduce the strain on the lateral (outside) tendons and ligaments of the limb. To further reduce the concussive forces on the inside sole and limb, the width of the outside branch of the shoe should be widened to aid in redistributing the load. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- After years of lameness issues and treatments that had limited results, I decided to remove the shoes off my then 14-year-old Warmblood mare. She has been barefoot since 2016 and had an excellent farrier that was doing the Bowkers trim. Things progressed positively and have just recently started her back to very light work. The farrier that I had been using moved and another has taken over the trim. Before starting her back to work she was on a 5-week schedule and her feet looked great, no longer crushing heels and landing flat instead of toe first. She remains on the 5-week schedule, but the hoof is flaring and by the start of the second week, becomes really flared and not the nice hoof shape I had before. The foot is widening and I feel she is crushing heels again. She is a big girl and I expect changes but concerned this could be heading in the wrong direction. My current farrier is also concerned as he now must come every three weeks instead of five. I consulted my veterinarian and thought X-rays would help determine if on track. Any suggestions? (View Answer)
It sounds like both you and your farrier are concerned with the recent change in appearance of your horse’s feet. Some horses are very sensitive to slight variations in trimming and shoeing. Radiographs (x-rays) would allow you to determine whether there are any imbalances that may be contributing to her recent change in hoof conformation. A radiographic shoeing consultation would allow your veterinarian and farrier to collaborate on what is best for your horse’s specific ailment.
Underrun heels are one of the most commonly encountered hoof abnormalities. Conformationally, the hoof will appear to have a long toe, low heel, and broken back hoof-pastern axis. Our first inclination is often to improve this axis with a wedge pad, however this may lead to further crushing of the heels. A more successful outcome might be achieved by aiming to redistribute the forces off of the heels, and providing more ground surface contact with the frog and bars. We have had some good success with the use of a “flip-flop” shoe. Although your horse is barefoot, it may benefit from this application for one or two shoeing cycles. This type of shoe has both a pad and metal shoe component. The pad component redistributes the overall forces on the bottom of the foot, and the shoe component is abbreviated and does not extend to contact the heels. With the heels predominantly unweighted, this can promote heel growth. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- What should I be feeding my horses for better hooves? What are your thoughts regarding horses going barefoot and the use of boots? (View Answer)
In a controlled feeding trial, biotine-supplemented horses had a 15% higher growth rate of hoof horn and dorsal midline hoof wall at 5 months compared to the control group. Cysteine and Methionine are also important components of the hoof wall matrix. Unfortunately, there is no external oversight for human or animal nutraceuticals, so it's important to go with a reputable company that does internal quality assurance. Nutramax Laboratories, the maker of Cosequin Equine Products, and Platinum Performance are two well-regulated companies.
In regards to going barefoot, that is completely dependent on your horse. Some horses do well barefoot, while others may become footsore. Barefoot farriery and the use of boots is largely dependent on your horse’s job, exercise level, riding surface, and hoof quality. It’s important to note that a barefoot horse still needs to have their feet trimmed on a regular schedule to maintain a healthy hoof. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- What can be done to help horses with thin soles? (View Answer)
For a horse with thin soles, your goals should be to reduce concussion and redistribute the weight bearing of the foot away from the sole. Vibration frequencies in the foot are significantly lower with the use of polyurethane and aluminum shoes, compared to steel shoes. In a structurally normal hoof, the application of a rim or full pad can help further reduce these forces. Viscoelastic pads have been shown to reduce the concussive forces in the foot by up to 75%. A pour-in-pad should not be used in horses with thin soles. Pour-in-pads disperse the polymer between the branches of the shoe and redistribute the weight bearing away from the walls and further onto the sole. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- My horse's hooves do not grow at a rate they should. When I purchased my horse a few months ago, he was quite overweight. Even though he has lost weight since then, he still has a few more pounds left to go. My farrier says it may be part of the problem (i.e. the extra weight limits blood circulation in his feet which prevents hoof growth). My horse has probably lost close to 100 pounds but still has another 50-75 pounds to go. What are your thoughts? (View Answer)
Hoof growth can be stunted by a multitude of different causes. Your farrier is correct, hoof circulation is affected by cyclical loading, which can be affected by weight. Whether or not this directly translates to your horses reduced hoof growth is unknown, but it may be a contributing factor. Insulin dysregulation can also occur when a horse is over-weight, similar to type-2 diabetes. Metabolic disorders can influence a number of different cellular tissues within the body and may also be involved.
Diet is another factor that can influence hoof growth. Over the course of 5 months, one study found that Biotine supplementation increased hoof wall growth rates by 15%. Cysteine and Methionine are also important components of the hoof wall matrix. Please consider consulting your veterinarian for further recommendations and a metabolic evaluation. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- I have a OTTB that ran too long (8 years) and has become lame due to confirmation issues that has left with issues with his P3 / P2 joints. He has been on and off lame over the last year. He's gone through a full Adequan cycle supplemented with Previcox. In addition, my farrier has developed a corrective shoeing method with wedge shoes on a short cycle to improve his P3 / P2 alignment. It's been a long road and I'm seeing improvement between bouts of lameness induced by abscesses... I'm treating the abscesses with guidance from my vet. Is there anything I can do proactively to prevent these abscesses? (View Answer)
Recurrent hoof abscesses may be the result of an underlying condition, such as Pituitary Pars Intermeda Dysfunction (PPID), also known as equine cushing’s disease. We are seeing PPID more frequently in younger horses that do not necessarily have the traditional clinical signs for this disorder. PPID can result in a weakened immune system and make horses prone to infection, including recurrent hoof abscessation. Another cause, if the abscess continues to recur in the same location, is the presence of a keratoma within the hoof capsule. These potential causes can be ruled out with hoof radiographs and bloodwork.
If there is not an underling systemic cause or ailment, your horse may benefit from shortening his trimming or shoeing cycle. Abscesses can occur for a number of different reasons and environmental conditions. Maintaining a clean environment and well managed hoof may reduce his incidence of recurrence. Another treatment that may be beneficial for your horse is the use of CleanTrax while soaking his hoof. Please discuss these considerations further with your veterinarian. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- My horse has sidebone in both sides of both front feet. A nerve block isolated pain to the palmar digital nerve but is symptomatic on the right front. Due to a previous shoulder injury, I am reluctant to try the wider, heavier shoes. What other trimming/ shoeing would you recommend? (View Answer)
Ossification of the collateral cartilages of the coffin bone, also known as sidebone, is infrequently associated with lameness. When lameness does occur, it is often related to the ligaments that attach to this ossified cartilage. Sidebone on a radiograph does not necessary mean that this is causing your horse’s lameness, even if it blocks to a distal palmar digital nerve block. There are a lot of other structures that could be involved and are more frequently implicated in lameness, such as the deep digital flexor tendon for example.
Your question regarding shoeing is further complicated by your history of a shoulder injury. Without knowing the specific structure that was injured and the exact cause of your current lameness it is difficult to make shoeing recommendations. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA
- I have a horse with low heels that tends to get thrush. Due to the farrier’s schedule, we were unable to get shoes on him in a timely manner. My horse had been at the trainer in which he had shoes placed, but by the time he came back home, he had outgrown the shoes and they had to be pulled. Would shoes help with the tenderness of his feet at this point? He is limited in his use due to his lameness. Is there a corrective shoeing method you would recommend for this situation? (View Answer)
The question is whether your horse has a low heel versus an underrun heel. A low heel may be conformationally appropriate for your horse. An underrun heel is one of the most commonly encountered hoof abnormalities where the angle of the heel is less than that of the toe. In this condition, the hoof wall at the heels will frequent roll inward and become crushed, which can result in lameness. When attempting to correct this condition, your shoeing goals should be aimed at redistributing the forces off of the heels, and providing more ground surface contact with the frog and bars. We have had some good success with the use of a “flip-flop” shoe which has both a pad and metal shoe component. The pad component redistributes the overall forces on the bottom of the foot, and the shoe component is abbreviated and does not extend to contact the heels. With the heels predominantly unweighted, this can promote heel growth.
If your horse’s lameness is also related to thin soles, most “flip-flop” shoe designs have pad material that is dispersed between the branches of the shoe. This type of design results in the horse’s weight being redistributed away from the walls and further onto the sole, which may result in further discomfort. A radiographic shoeing consultation would allow your veterinarian and farrier to collaborate on what is best for your horse’s specific ailment. Additionally, a shorter shoeing cycle may improve your horses hoof quality and recurrent thrush. If your horse’s current farrier is not available, your veterinarian may be able to direct you to another farrier that you could work with in your area. Jillian Mills, DVM, DACVSMR, CERP, CVA, Starwood Equine Veterinary Services, Woodside, CA