Updated on 09/15/2011 12:33PM

Building a sounder racehorse with silicon

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LEXINGTON, Ky. - The holy grail in racing is to balance athletic talent and soundness, and too often unsoundness undermines ability. But a recent study may lead researchers toward dietary solutions in the quest to build a stronger racehorse - or at least allow horses to maximize the strength and growth of their bones.

In a study that will be published in the Journal of Animal Science, Michigan State University scientist Dr. Brian Nielsen found that feeding silicon, a mineral that's commonly found but not easily absorbed by horses, may help horses build and retain bone.

Horses generally receive an adequate supply of silicon through grazing and feed, but in a small sample of 12 broodmares who had recently foaled and 12 yearlings, Nielsen found some advantages to feeding additional silicon.

Nielsen's team mixed a powdered silicon supplement, designed for easy gastrointestinal absorption, in the feed of six of the yearlings and six of the broodmares for 45 days.

At the end of the study, the supplemented broodmares showed increased concentrations of osteocalcin, the biochemical marker for bone formation. The supplemented yearlings, meanwhile, showed lower concentrations of ICTP, the marker for bone resorption, an indication that the young horses were retaining bone substance for longer even as new bone was being "built" by their bodies.

Nielsen's work is still in its early stages, but these preliminary observations provide some hopeful signs that adding digestible silicon supplements to a horse's feed could help strengthen his bone development.

In another study due to start later this month, Nielsen will explore the role of exercise in enhancing bone strength - an issue he has studied previously in calves.

In the upcoming six-week study, Nielsen will compare bone mineral increases and decreases in the cannon bones of three groups of weanlings: some stall-confined, some required to sprint about 100 yards once a day for five days, and some turned out in a paddock.

In the calves' legs, Nielsen said, "we saw more mineral being added to the front of the bones, so the bones were getting thicker. We also saw the bones' shape change so the bone was more resistant to bending."

If similar results occur in horses, Nielsen's study could shed light on how early training programs, especially exercise that encourages bone to respond to force rather than repetitious motion, might promote bone growth to adapt to the stress of high performance.

Hemlock still under suspicion

As research continues, Kentucky's wave of mare reproductive loss syndrome remains a mystery. And recent test results that appeared to eliminate one potential culprit, poison hemlock, may not have proven much at all, according to a USDA toxicologist.

Researchers at the University of Kentucky are investigating a number of potential causes for the syndrome, which caused at least 1,200 early- and late-term abortions in area broodmares since late April. The leading theory still appears to be cyanide from cherry trees near mares' pastures, possibly delivered to horses via caterpillars. UK scientists also are considering mycotoxins, phytoestrogens, and ergot alkaloids as causes.

Another theory, proposed by a Clemson University team, that the mares aborted after eating poison hemlock in fence rows, appeared to be put to rest after the USDA's Poisonous Plant Research Laboratory in Logan, Utah, reported that affected horses' blood, urine, and tissue samples tested negative for hemlock's telltale coniine alkaloids.

But USDA toxicologist Dr. Kip Panter, who coordinated those tests, says negative results don't mean hemlock can be thrown out as a potential cause or aggravating element.

"It's all dependent on when these samples were taken and sent to us," Panter said. "By the time the fetus ends up on the ground and is submitted for necropsy, my suspicion is the alkaloids are already gone."

To establish a life-span for the elusive alkaloids, Panter's lab is conducting a test on a few mares to determine how long hemlock alkaloids remain in their system after they eat the plant.

"My suspicion is that after about 48 hours it's gone," he said.

"Hemlock might be a factor in the scenario, but I am a little skeptical," Panter added. "This might be one of those undiagnosed syndromes that scares you, because you don't know when it might jump up and get you again."

Whether or not hemlock is fingered as a factor in MRLS, the possibility may have helped launch a new research project into the poisonous plant.

"There's not much research into it, because horses are so expensive to use in research," Panter said. "But we've talked about doing a study of hemlock in pregnant mares for years, because we know it causes birth defects in other animals. This could be a time to do it."