Equine Colic is the most common medical ailment in the horse. Over the past 25 years there have been great strides in both the prevention and treatment of equine colic. Improvements in deworming products and schedules, equine dentistry, and management practices have helped to reduce the number of horse colic cases. Advances in veterinary knowledge and the development of new drugs and surgical techniques have helped to improve the survival rate for horses suffering with equine colic. Still today, each year 10-11% of the horse population suffers from colic. One of the causes of colic, sand ingestion, can be a substantial risk to certain horses and sand colic is not uncommon in many areas of the country. Horses ingest sand either through grazing or eating hay or grain from the ground. The problem is most prevalent in the semi-arid west and southwestern states and the coastal states, although it can be a problem in any state. Soil or “dirt” consists of a certain amount of sand, which is a naturally occurring finely divided rock. In fact, many soils not only contain sand, but also contain silt which is an even finer particle of rock and some contain gravel which are the rock particles that are larger than sand. The silt, sand and gravel ingested must travel through the digestive system of the horse to be removed within the feces. One of the problems associated with this situation is that the sand and gravel and to a lesser degree the silt can produce irritation within the digestive system. Additionally, in certain situations the sand can accumulate within the digestive system and the irritation can intensify due to this accumulation. As sand accumulates in the intestinal tract, a combination of the irritant effects and the weight of the sand can lead to impaired motility, reduced absorption of nutrients including water and thus, digestive upset. If the accumulation of sand continues, the resultant digestive upset will eventually lead to poor condition, diarrhea and eventually sand colic. Making the situation even more troubling is the fact that clearance of the sand from the large colon, where most sand accumulates, requires adequate gastrointestinal motility. So once the sand begins to collect in the colon, any resulting reduction in motility will further add to the horse’s accumulation of sand and gravel.
As mentioned above the signs of sand accumulation can include poor condition, difficulty in maintaining weight, diarrhea and equine colic. Since none of these conditions are unique to a sand accumulation problem, the owner seeing any or all of these signs cannot assume that the cause is sand. Sand accumulation can at times be diagnosed and there are four methods for this diagnosis, two of which are not conclusive and two of which are. The easiest of the methods, since the horse owner can perform it, is the fecal floatation test. With this method feces are collected from the horse and a standardized amount is added to a container with water. The water and feces are mixed so that any sand within the feces is suspended within the mixture and then allowed to settle to the bottom of the container. Once the sand has settled in the bottom of the container, the sand can be quantified. Although many veterinarians suggest this method and it has historically been considered to be one of the best in field tests, it has limitations. The test by design will inform you the horse is passing sand through his digestive system. The test will not tell you if the horse is accumulating sand within the digestive system. If some amount of sand is detected in the feces, it could be that the rate of ingestion and the rate of sand passage is equal and the horse is not accumulating any appreciable amount within the colon. On the other hand, if the rate of ingestion over a period of time outweighs the rate of sand passage, the horse begins to accumulate sand within the colon. Once this accumulation begins there is a likelihood that the sand will impair motility within the colon and additional accumulation will ensue. If no sand is detected using this test method one must then wonder if the horse is accumulating sand, because none of it is being passed in the feces. If very large quantities of sand are detected within the feces one can assume that the horse does have a sand problem. So although this test is used, the results are often hard to interpret and should always be scrutinized.
The second method, which is most commonly performed by a veterinarian, is to listen for sand in the colon. Utilizing his stethoscope your veterinarian can listen to the contractions of the colon within the abdomen and under certain conditions can actually hear the sound of sand moving within the colon. When the veterinarian discovers this sound and diagnoses a sand condition the results are considered reliable. Where this method encounters a shortcoming is when the sound is not detected, yet there is actually sand within the bottom of the colon. This can occur if the sand load is not moving either because the sand has impaired motility of the colon itself, or the normal motility within the colon does not have the force to move the sand and thus create the sound.
The two methods that are completely reliable for sand detection and the prevention of sand colic, are not readily accessible and are both quite expensive. The first method is to radiograph the abdomen and diagnose the sand load based upon the radiograph results. Equine abdominal radiographs must be performed in a hospital or clinic, with a radiograph generator that is powerful enough to penetrate the equine abdomen. Although this method is non-invasive it is inconvenient and incurs considerable expense. Furthermore, although considered to be reliable, some doctors have questions as to the sensitivity (ability to detect the sand) of this test, when the sand is spread over 70-100 feet of intestines. The last method although possibly the most reliable, is not only impractical for many reasons, but it is also invasive and expensive. Exploratory abdominal surgery although totally reliable in detecting sand, is only chosen with a horse ill enough to undergo colic surgery to relieve the condition.
It is recommend that if your horse is exposed to eating sand or dirt, the first step is to control the consumption through management changes. These changes include feeding, both grain and hay, only out of feeders, feeding off the ground and using mats in the feeding area. These steps will all help to control the sand intake. When feeding outside in a dry lot or a sparsely vegetated pen or pasture, covering a large area with mats, will help control both the eating area and the surrounding area where the horse is likely to browse for every last morsel of hay. These control measures will help in many cases, yet there are situations in which it is either hard or impossible to control the consumption of sand including herd pasture management, dry-land pasture grazing, and various other housing arrangements. For horses that do consume some quantity of sand, if complete control of sand intake is not possible, sand removal treatment with psyllium is a viable option. Historically there have been four problems with most psyllium treatments, not enough psyllium within the product administered, not enough product administered at each dosing, not a long enough or regular enough treatment period, and the lack of clearance due to altered colonic motility. There is a new, pelleted psyllium product that has just become available, called Assure Plus®, and this product works to overcome the common shortcomings of prior psyllium protocols. The investment in management changes and Assure Plus® treatment can result in a healthier horse as well as a horse less prone to equine colic.