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MSU professor and researcher, Dr. Bob Bowker, has researched the horse's feet for over 20 years. Bowker in 1990, began focusing upon understanding how nerves aid and improve foot function, how horses use many sensations present in the foot to negotiate within its environment and how the foot dissipates energy and supports the horse during health and disease. Osteoporosis in the horses foot comes on the heels of an upsurge of interest in unexplained equine lameness.
Q: What brought you to research osteoporosis in the equine foot?
A: We happened to notice 6 years ago when we were reporting to the AAEP on navicular syndrome that the coffin bone of these navicular horses had 1/3 less bone than other horses. I have a student (Tara Jackson from Australia) working with me; she and I see more and more of these horses, who go to necropsy for reasons other than foot problems. They have varying degrees of osteoporosis. We’ve been recording the breeds and ages; there does not seem to be a relationship to age. However, if they have been shod, there’s a greater chance for osteoporosis to occur in the older horse when compared to a barefooted horse.
Q: Are you able to differentiate whether horses have been barefoot or shod?
A: A peripherally loaded foot can occur in both shod and barefoot horses (if you let a barefoot hoof get too long). We have some horses who died in their late 20s who have never been shod and their coffin bones are more dense.
Q: For horses who are shod and stall-kept, is there an opportunity for a foot to regenerate any of that bone?
A: I think there is. We’ve just sent off a paper where we’ve been measuring the pastured horse vs. stalled horse, and a pastured horse averages 8000-10,000 steps per day. Horses stalled average maybe 800 steps per day. Bottom line: Circulation to and through the bone is crucial.
Q: Is uneven wear of coffin bone related to how the horse was trimmed?
A: The foot is adaptable…I don’t believe the horse’s foot is designed so 100% of the load is on hoof wall. When trimming, or adding shoes, the profusion of the foot will decrease; this is when you start to get changes in the foot as well as the bone.
Q: Are smaller hoofed horses more susceptible?
A: They can be, due to the smaller surface area and weight. Out in pasture, they may be able to load their sole surface more.
Q: To encourage pressure over entire sole area of the hoof, is it wrong for us to pick out feet?
A: The frog does not like constant pressure; it wants pressure and release. The frog can atrophy, so picking out periodically (daily) helps the frog maintain its normal purpose.
Q: For a horse who is chronically lame, what is your recommendation?
A: I would wager that by loading the sole more, getting him on a conformable surface (ideally, “pea” gravel, 1/4 to 3/8 inch smooth stones) and having him out moving 24/7, you might see improvement.
Q: What advice can you offer people whose horses must be stalled? Pull the shoes? Give the horses time off?
A: Put them on a surface that allows the sole to become supportive. Hooves become less of a weight-bearing structure if a horse is out moving more. The longer they are barefoot, this allows the foot to recover.
Q: What is your hope for this research?
A: I’m starting to come to the conclusion that integrity of the coffin bone is one of the major keys to the good foot. Mother Nature’s going to balance the load on whatever you provide. It’s like sneakers vs. high heels. You’re more comfortable when your weight is on a greater surface area. Loading from sole surface, engaging the frog and bars, you’ll develop a stronger support structure, so other problems will become less and less.
Robert M. Bowker, VMD, PhD, is a professor and researcher at the College of Veterinary Medicine at Michigan State University. He recently opened the Corona Vista Equine Center in Michigan, www.coronavistaequinecenter.com