White adds that course roughage with low digestibility or particularly course fiber can cause impaction colic, while horses
fed Bermuda grass have an increased risk of ileal impaction. Grain overload increases colic risk. Overfeeding on lush grass,
especially clover, may cause tympany; alfalfa hay, reduced hay quality/digestibility and feeding from round bales have been
implicated as well.
Changes in feeding practices, i.e. a sudden increase in grain, changes in type of hay or grain, or greater than 5-kg concentrate
per horse per day, have been linked to increased colic risk, as well as feeding of pelleted feeds and sweet feeds, compared
to no grain at all.
Lower in fiber, grain diets have been shown to decrease colon water content, due to lesser ability to bind water. Grain also
is said to increase gut gas production, predisposing to tympany, distention and displacements.
What seems basic to these feeding practices and association with colic is dietary change as well as deviation from feeding
the horse because the animal would naturally graze in open pasture. In some cases, it was noted that feeding grain soon after
being brought in from pasture increased risk, while keeping horses out on pasture while feeding grain decreased risk.
While one can properly feed horses by incorporating concentrate to its diet, the basic need for about 1.5-2.0 percent roughage
is important. Nibbling eating behavior on lush pasture, and without abrupt dietary changes, if hay is also available, decreases
In some studies, feeding small amounts of grain at frequent intervals has been reported to decrease the large-colon water
shifts. Though one study showed that feeding grain more than twice daily was related to increased colic risk, the total amount
of grain consumed may have been the culprit rather than the frequency of feeding.
Several studies have demonstrated that access to pasture and increased opportunity for grazing are related to reduced risk
of colic, while one study associated increased hours of stabling with increased risk.
The major concern associated with pasture and increased risk of colic is grass sickness or overindulgence of fresh lush spring
As opposed to various time periods turned out to pasture, it was shown that spending 100 percent of time in a stall was significantly
associated with increased risk of colic (in one study), and that horses having less access to pasture were at risk to colic.
Confinement has been shown to be both a positive and negative influence on colic risk. According to White, a VMRCVM study
showed that housing and confinement on farms in the area were not a colic risk factor, while other studies showed that increased
confinement and reduced activity may lead to higher risk of cecal and large-colon impaction.
Cohen proposes that even with the epidemiological information already considered, new statistical and epidemiological models
"are needed to address the many deficiencies in our knowledge about the causes of colic in horses.
"Statistical models that might be applied include principal-components analysis and related methods or neural networks, which
may provide a method for better defining the simultaneous contributions of groups of variables contributing to colic, the
complex pathways by which predisposing factors may result in colic, or both," Cohen says.
"Epidemiological models other than the risk-factor-identification approach that is currently dominant, or more communal-based
approaches, may be needed," Cohen adds.
While the majority of clinical cases of colic are based in the general horse population, most of the studies investigating
the possible cause(s) have been conducted at universities and teaching hospitals. It's another concern, Cohen adds, because
results from such studies may have limited applicability to the general horse population.
Information is needed from private-practice clinicians, which may be more representative of horses and colic incidence. "Collecting
reliable data from practitioners selected in an unbiased manner could provide extremely valuable information," Cohen suggests.
"We will never eliminate colic in horses, but I do believe some can be reduced by better management. And more data are needed
to establish practices and circumstances that are risky or salutary," Cohen adds. "This will require both funding and effort."