This big round rock is an enterolith surgically removed from the intestine of my friend's horse Hapsburg. Off and on this summer 'Happy' had shown signs of colic, which would quickly resolve with some banamine and hand walking.
Happy is a 17-year-old former race horse (a stakes winning Thoroughbred). After his racing career ended, he was retrained for dressage and my friend competed with him through the first level.
Happy has a distinctive thoroughbred personality. He is playful, sensitive and intelligent. His intelligence has caused all sorts of problems in his human interactions. For many years Happy would go up rather than forward. It was frightening to his owner ride him in his upward moments -- and breathtaking too. Bolting, hopping and skipping were a large part of his repertoire as he sought to defy gravity -- a part of his playfulness.
Over the years, Happy has calmed down to a degree. He has become arthritic (caused by his racing career) and less able to 'cut up' when he felt like it. He had hoof problems -- going barefoot at one point.
By the time he wound up at UC Davis, he had been uncomfortable for several months off and on. His owner was afraid he had a tumor. When an X-ray could not pinpoint the source of the problem, the vets at Davis suggested exploratory surgery.
The word enterolith is derived from the Greek word 'entero' meaning intestinal and 'lith' meaning stone. An unusually high number of these intestinal 'rocks' occur in California and the southwestern regions of the United States.
According to Diana M. Hassel, DVM, equine surgeon at UC Davis, enteroliths are reflective of the mineral composition of soil and feed materials in the region. "Structural and chemical composition analysis indicates that enteroliths are composed primarily of magnesium, ammonium and phosphate. The combination of these three elements into a crystalline form is commonly referred to as struvite." Struvite stones form the urinary tract obstructive stones in cats, dogs and in humans (although 85 percent of kidney stones in humans are made of calcium). Stuvite stone formation is also mainly an indication of infection in cats, dogs and humans, but this is not true of horses.
Happy's stone is a little larger than a coconut, nice and round, a lovely green color (with darker green swirls) and weighs a little more than five pounds. It is cool to the touch and very smooth. Looking at a drawing of the equine intestine gives one pause to think about how it slowly formed (most enteroliths take only two years to grow) and how it must have rattled around in his stomach, trapping gas and giving him pain.
Given that the equine intestinal tract has evolved little over 50 million years, as herbivores (at several points early horses were also fruit eaters) it is a wonder that all sorts inedible things don't wind up in the horse's gut. Fortunately horses are selective in their eating habits and prefer the tasty grasses to rocks.
Because the horse has a small stomach, it must eat regularly to maintain weight, maintain the motility of the 'gut' itself and keep up its energy. Horses on pasture tend to be more continuous in their foraging than ruminants (72 percent of the time in a 24-hour is spent eating -- this is higher in feral or wild horses). Stalled horses fed twice daily spend about 13 to 14 percent of their time foraging and this is where stone formation comes in.
Risk factors for enterolith formation include dietary and genetic factors. The stomach must have an alkaline PH. A nidus (foreign material providing a central core for the enterolith) must form. Conditions for low motility in the colon (caused by confinement) must also be present.
In California the mineral content of the water and alfalfa exceeded the recommended magnesium requirements for horses. In addition to this, alfalfa may cause excessive amounts of free ammonium to be released into the large colon. Bran feed contributes phosphorus to the gut. All these minerals together combine to form stones (struvite).
Genetics also may be a factor in stone formation. Dr. Hassle has also discovered that 8.4 percent of horses with enteroliths had siblings that were also affected. Arabian horses were the breed most commonly diagnosed. Arabians and Arabian crosses comprised 40.3 percent of the horses treated at UC Davis with enteroliths. Other breeds that may have a genetic link to stone formation were Quarter horses, Thoroughbreds, Appaloosas, Morgans and American Miniatures.
The clinical signs of enteroliths are subtle. Thirteen percent of horses with enteroliths had a history of passing stones in their poop. Behavioral signs included: lethargy, depression, cranky behavior, weight loss, occasional loose stool and poor performance or reluctance to jump or go down hills. Horses with large stones (like Happy's) formed in the large colon, commonly have a history of chronic colic. "Horses with the smaller stones that become lodged within the small colon are less likely to have a history of colic." The smaller stones are the deadlier they are. Small stones do not create a big complete blockage of the colon so the signs of severe colic are slow to manifest. Because the signs of distress are slow in coming, the small stones are also more likely to be discovered after they have ruptured the bowel. Once a rupture occurs, the horse either dies or has to be euthanized because of infection.
According the Dr. Hassel, the only successful treatment for horses with colic due to stone formation is surgical removal. The treatment success rate at Davis is 90-95 percent. Discovering the stones before they perforate the bowel is the challenge.
Happy survived his exploratory surgery and has managed to fully cooperate with the daily hand walking -- a minor miracle -- part of his recovery treatment. He seems to know that he just got a second chance on life.
Facts for this post were taken from Equine Enterolithiasis: A Review and Results of a Retrospective Study.
This is amazing. Thanks for the picture, I used it for a graduation exhibition at my high school. I'm glad ur horse survived! =]
Posted by: Haley | November 23, 2008 at 07:06 PM
WOW!
That is an amazing specimen! Very lucky horse too :)
Just wondering if it would be at all possible if I could get in touch with your friend who owns it?
Posted by: Jennifer | June 18, 2010 at 12:44 AM