Because one of my ponies suffers from mild recurrent colic and because three different veterinarians have been unable to find anything wrong, I’m always on the lookout for an explanation for this frustrating repeating problem. An article in the January 2014 issue of Equus magazine described one possible trigger for mild recurrent colic.
Enteroliths are “rock-like concretions…that form in the large intestine.” (1) Sometimes an equine can carry hundreds of small ones or develop one or a few that grow as large as a melon. “The stones might remain in place for years while causing few, if any, outward difficulties. Or, they may trigger intermittent mild colics, collecting to cause an impaction and then shifting away to allow the intestinal contents to pass by once again. In the worst-case scenario, an enterolith becomes lodged in a spot that completely blocks the intestine, creating a life-threatening obstruction that requires emergency surgery.” (1)
Enteroliths begin with some small object like a grain of sand or piece of twine over which minerals are deposited. They are typically formed in a wide part of the colon; it’s when they grow larger than the downstream portions of the colon that they become dangerous. Unfortunately at this time, presurgical diagnosis is at best a 50/50 proposition.
While precise diagnosis can be challenging, four risk factors have been identified:
- Higher than average pH in the right dorsal colon. This is often associated with a diet containing alfalfa.
- Genetic predisposition. Arabs, Arab crosses, Appaloosas, Saddlebreds, Morgans, Miniature Horses, and donkeys have all been found to be more predisposed to enterolith formation.
- Higher mineral concentration, especially magnesium, in the colon. While alfalfa is often cited as a source of excess magnesium, water may also be a source. “Researchers speculate that some high levels of minerals, especially calcium and magnesium, in the water may contribute to enterolith formation.” (2) And while enteroliths have been reported across many states and countries, more cases have been reported in the Southwest and California. “[Hays] and other feeds, especially alfalfa, grown in these regions tend to be higher in minerals.” (3)
- Slower gut motility. Some equines may be genetically predisposed to food moving more slowly through their system. Decreased exercise and decreased access to forage also contribute to slower transit times for feed.
Of these four risk factors, two are relevant to my pony. We use well water here, and it does have enough minerals to leave a crust on pans in our kitchen when we heat it. Colorado is considered part of the Southwest where hay may be more highly mineralized. Slower gut motility seems even more relevant, though I was surprised the article didn’t mention age – I would think that older ponies have slower gut motility than younger ones.
My pony’s symptoms do seem to be triggered by changing her feeding regimen in a way that slows gut motility. When I switch from my normal four-times-a-day feeding schedule to two-times-a-day, she often develops symptoms. A hay net to slow her feeding has helped with this problem (the most recent issue of The Partnered Pony™ Inquirer discussed slow feeding easy keepers; click here to read an excerpt.) Yet the thing that has helped most is feeding senior feed twice a day, as I mentioned in my last post on this topic.
I of course could relate to the article’s statement that precise diagnosis is difficult. One thing the article mentioned, though, that I haven’t done, and the vets didn’t suggest, is to examine her manure to see if stones are present. I imagine the vets didn’t mention it because it wouldn’t change the recommended treatment. I may do the exam, though, just to address my own need for an explanation for this frustrating situation.
- 1) Bonner, Laurie. “Understanding Enterliths,” Equus, issue 436, January 2014, p. 49.
- 2) Bonner, p. 55.
- 3) Bonner, p. 54.
© Jenifer Morrissey, 2014