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Shoes And Hoof Circulation: Is There A Connection?

Specific shoes are often recommended by veterinarians to aid horses facing a variety of issues, from abscesses and lameness to musculoskeletal issues and environmental conditions. These shoes affect the horse's hoof in a variety of ways. A Polish study evaluated how two different types of shoes may affect hoof circulation.

Dr. Marta Mieszkowska and a team of researchers used thermography to measure distal limb temperatures on 16 Warmbloods that had been diagnosed with navicular bone changes or deep digital flexor tendon (DDFT) injuries. The horses were divided into two groups: the navicular horses were shod with egg-bar shoes and the DDFT horses were shod with wedge pads.

The egg-bar shoes shifted the horse's weight to the rear of the foot and increased the sole surface. The team noted that the shoes may compress blood vessels and adversely affect soft tissues.

The study showed that since w edge pads force the horse's coffin joint into a more-flexed position, they could increase pressure on an artery while reducing the load on the DDFT.

The research team determined that egg-bar shoes decreased the median temperature of the heel portion of the hoof. Wedge pads decreased the median minimal temperature in the heel and toe of the hoof.

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The authors concluded that horseshoes may have a negative impact on blood circulation in the hoof, and noted that different types of shoes may result in different temperature differences.

New Test Can Detect Bisphosphonate Three Years After Administration

A new study may give regulators the key to better regulate bisphosphonate use in racing. Controversy has surrounded bisphosphonate use since the drug became approved by the Food and Drug Administration (FDA) for use in horses. Bisphosphonates are labeled for adult horses battling navicular syndrome and similar chronic conditions that don't respond to other types of treatment.

The FDA has licensed two bisphosphonates, which are sold under the trade names Tildren and Osphos. The Horse reports that there are other, non-licensed versions of bisphosphonates marketed for horses which are not FDA-approved. Those non-approved products are advertised as being more powerful than the two approved versions.

The FDA prohibits the use of bisphosphonates in horses younger than four years old, but some owners and trainers continue to use the product off-label on young horses. Bisphosphonates impact the build-up/breakdown cycle in bone, which veterinarians say could have negative effects on growing animals.

Dr. Christopher Riggs, chief advisor in veterinary science at The Hong Kong Jockey Club, studied 24 Thoroughbreds who had received a single therapeutic dose of tiludronate disodium between one month to three years earlier. The research team then tested blood plasma and urine samples using ultra‐high‐performance liquid chromatography high‐resolution mass spectrometry, a new testing technology. The tests found traces of tiludronate disodium in every sample.

Previously, testing was only able to detect bisphosphonates in equine blood or urine if it had been administered in the last 40 days. Hair testing could detect an administration from months prior, but is limited in its ability to pinpoint the time of administration.

Researchers believe the drug lingers on the surface of bone, occasionally releasing back into the horse's body for months or years, but little is known about how long that effect could go on. The drug may be more detectable in horses that are going through training and rest periods that affect bone remodeling.

Bisphosphonate Use In Young Horses The Focus Of Texas A&M Study

Texas A&M researchers have created a study to evaluate off-label bisphosphonate use in horses. Originally meant to mitigate navicular pain in mature horses, off-label use of the drug in younger horses may promote bone degradation.

Though the number of equine fatalities from horse racing is decreasing, California, Kentucky, and New York have seen increased racing fatalities in 2018. Lead researcher Dr. Jessica Leatherwood says that a primary concern regarding these breakdowns is the off-label use of bisphosphonates; the study will assist in determining the effects of the drug on developing skeletons.

There is currently no scientific data exploring the effects of bisphosphonate use on young, exercising horses. The study, “Bisphosphonate Pharmacokinetics and Comprehensive Effects on Juvenile Cartilage, Bone Growth and Healing: Implications for Animal Welfare,” received a $500,000 grant from the U.S. Department of Agriculture's National Institute of Food and Agriculture. The particular bisphosphonate that will be studied is clodronate disodium, which is easy to administer and popular.

Racing commissions acknowledge the off-label use of bisphosphonates, but laboratories are unable to reliably test for the drug, limiting the ability to regulate off-label use.

Radiographs are often a key to racehorse sales, particularly in young horses where they expose skeletal health. Off-label use of bisphosphonates may mask potential flaws and cause microdamage accumulation, which could lead to breakdowns. The concern over bisphosphonate use isn't limited to racing; some sport horse disciplines are also limiting or restricting their use.

Horse and sheep models will be used in the study. As sheep are typically processed before they are two years old, they will offer insight into the potential changes in bone and biomechanical properties. The team hypothesizes that younger animals will clear the bisphosphonates more rapidly than older animals, that the drug alters bone in young, exercising horses, and that it will also have anti-inflammatory effects on the joint.

The findings could help shape new regulatory policies on bisphosphonate use in young horses.

Maybe She’s Born With It: Navicular Fractures May Not Be Trauma-Based

Scientists in Belgium and the Netherlands have discovered that abnormalities in the navicular bone that cause lameness may not be related to trauma — some may be genetic. Partitioned navicular bones are often confused with fractures and assumed related to wear or injury.

Drs. Ellen van der Zaag, Erik Weerts, Antoon van den Belt and Willem Back documented three cases of navicular bone partitions whose sections are defined by defects in the bone, covered in smooth cartilage and vary from full separation to shallow indentations. Each was discovered when the lame horse had X-rays taken.

These abnormalities aren't injuries, the researchers note: they are present at birth and could be seen if X-rays were taken before the horse became lame. The researchers believe that these areas are caused by a disturbance in blood vessel arrangement as the bone transforms from cartilage to bone. The partitioning typically develops in two specific areas: one-third of the width of the bone from either end, where blood vessels converge.

The partitions in the bone weaken it. As a horse grows and enters work, these partitions may develop cysts as damaged areas begin to die, making the horse lame. If the condition is found before the horse becomes lame, then corrective trims and shoeing, restricted exercise, and nonsteroidal anti-inflammatory use may help preserve the horse's soundness.

However, the prognosis for soundness is poor even when these tactics are employed. A neurectomy, where the nerve is surgically severed, isn't recommended as it would accelerate cyst formation and increase fracture risk.