Noteworthy: 11/03

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Topical Capsaicin Relieves Pain Over Heels
We already know that the newer topical capsaicin creams give considerable pain relief. A recent study performed at the University of Illinois College of Veterinary Medicine and published in the Journal of Veterinary Internal Medicine shows it can also be of use when applied at a distance from the source of pain, over the nerves carrying pain sensations from that area.

In a model of foot pain, seven horses were shod with a heart-bar shoe that could be adjusted to apply sufficient pressure to produce a grade 5/5 lameness (nonweightbearing, “three legged lame”). An hour after inducing the lameness, capsaicin cream was applied to the back of the pastern over the medial and lateral nerves supplying the foot. In the treated horses compared to untreated, significant drops in heart rate, a nonspecific measure of pain, and also in lameness grade were noted, beginning 20 to 40 minutes after application and lasting up to 3 1/2 hours.

These results suggest topical capsaicin over the heel nerves is worth trying as an alternative to bute in horses with navicular, laminitis or other types of foot pain. For ringbone or laminitis pain, the cream should be applied higher up, at about the level of the ends of the splint bones, to make sure you also get the nerve branch supplying the front of the foot, or could be rubbed in 360 degrees around the pastern.

While capsaicin effects can be seen after the first application, the result will peak after two to three days of use. Apply three to four times day for the first two to three days and if a desirable level of relief is seen, continue using it one to two times daily. (See September 2002 for our capsaicin-product field trials.)

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Bone Scans Need Interpretations
Bone scanning is a sensitive method of detecting areas of active inflammation or infection and especially helpful for hard-to-X-ray areas, like the back. However, a study from the Norwegian School of Veterinary Science suggests some care might be needed in interpreting results.

A total of 33 normal and completely asymptomatic riding horses had their backs scanned. One or more areas of increased uptake were commonly found in the thoracic spine, between T13 and T18. This corresponds to roughly the back edge of most saddles, and the area immediately behind it.

This study reinforces once again that as wonderful as high-tech diagnostics are, the diagnosis of a problem can’t accurately be made on only the results of an X-ray (or bone scan, etc). Accurate diagnosis requires an evaluation of findings on physical examination, owner description of symptoms, watching the horse move and nerve blocks when indicated. (See August 2002 for bone scans.)

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Genetic Link Found To Equine Allergies
Researchers at the University of Zagreb in Croatia report a possible link between genetic makeup and allergies. A total of 448 Lipizzan horses were tested for their levels of IgE, an immunoglobin associated with allergic reaction, against specific Aspergillus mold antigens. These levels compared to genetic markers. The researchers found a strong correlation between the specific IgE levels and gene markers.

This is an exciting breakthrough, as similar techniques may reveal why certain breeds or lines are prone to allergy in general, or even hypersensitivity to specific allergens, such as the marked sweet itch/Culicoides sensitivity in the Icelandic breed. More research could be of significant use for improving breeds.

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Equine Athletic Ability
A horse’s maximal oxygen consumption, which is a measure of his ability to perform work aerobically, can increase up to 30 times the resting level when he exercises, which is up to 2.5 times more than any other animal of similar size.??Small wonder that any damage to or abnormalities in the respiratory tract can have a large impact on the horse’s exercise capacity.??However, the question of how the horse can manage to deliver such a large increase in oxygen to his lungs has remained a puzzle.

An Italian study published in the European Journal of Applied Physiology may have the answer. The study showed that the horse can increase the cross-sectional area of the entry into his larynx during inhalation by up to four times its resting size.?? This greatly reduces the resistance to air flowing into the lungs and helps explain why the horse is such a uniquely phenomenal athlete.