Sand colic is a common problem for horses living in areas with loose, sandy soils. It is caused by the accumulation of sand in the horse's gastrointestinal tract (GIT). Horses consume sand from eating hay off of the ground, grazing in pastures, and when drinking from shallow mud puddles. On occasion, some horses are known to deliberately eat sand for unknown reasons.
As horses graze in paddocks containing sandy soil, they often will inadvertently ingest sand that may be present on the roots and other parts of the vegetation. Over time, this repeated ingestion of sand particles can lead to a blockage in their gastrointestinal tract, resulting in colic. The exact amount of sand required to cause a problem is not known, as it varies in each horse. As little as 8 kg of sand accumulation in some horses has required colic surgery due to sand impaction.
During the early stages of sand colic, horses' fecal output may be normal, and the feces may or may not show evidence of sand within the texture. As the condition progresses, and the obstruction worsens, affected horses may show decreased fecal output or it may cease altogether. Diarrhea may occur a couple days prior to onset of signs of colic.