Does Bermuda Grass Hay Cause Colic?
Ileal-cecal impaction has been associated with diets consisting of Bermuda grass hay, which has led some individuals to advocate that the hay should not be fed to horses. Symptoms of ileal-cecal impaction include mild to sever colic with obstruction of the intestinal lumen at the junction of the ileum and cecum. See diagram below. Treatment of ileal-cecal includes colic management, although it may even require surgery. There have been suggestions that dry forages or hays, which are high in fiber, may be a factor in causing the condition however, the association of the hay with impaction may be secondary. The impaction that develops may be secondary to spasmodic contractions of the ileal musculture against the ingesta in the lumen of the gut. There are numerous factors that could lead to some type of gut response, including more severe spasmodic contractions.
Empirical data on the frequency of ileal-cecal impaction in horses is not available, but comparison of hospital caseloads would suggest that the incident of this ailment is much less than the occurrence of other forage related diseases, such as enterolith formation and fescue toxicity. Reports have included rapid changes in types of hay fed, such as replacing alfalfa hay with Bermuda grass hay. Alfalfa hay is leafy, significantly higher in protein, depending on the hay maturity usually lower in fiber, and more easily digested than Bermuda grass hay. Reducing the horse’s protein intake (thus reducing the nitrogen intake) will influence the bacteria population in the gut, which is one of the reasons horse owners are always encouraged to make diet changes gradually. Additionally, sudden disturbances to the microflora population can insult the digestive process thus adversely influence gut integrity subsequently leading to colic conditions.
Another consideration is that alfalfa hay contains more protein than a horse requires. Feeding less alfalfa by changing hay type and portions will reduce protein intake and thus reduce the nitrogen content of the diet and intake. Mammals are designed to eliminate nitrogen via the urine; less dietary nitrogen intakes results in less urinary nitrogen, which means less water is needed to remove the ammonia waste product. Thus the horse consumes less water. There is nothing wrong with this physiological adjustment, but water is also important in lubricating the gut as well as promoting the passage of digesta in the intestinal tract.
The nutritional management of forages relative to impaction is a critical issue, which should emphasize the importance of the guidelines for diet adjustments listed in the Feed Consumption Guidelines for Horses, REB Fact Sheet # 112. Colic continues to be the number one concern of horse owners and appropriate nutritional management of our horses’ diets can reduce the triggering factors that are associated with colic-type syndromes, such as ileal-cecal impaction. Bermuda grass hay is one of the forage options that horse owners have to feed to their horse. As with all forages whether it’s from pasture, bale hay or pellet/cube hay, nutritional management is perhaps the most important factor in managing potential concerns.
[Note: Schematic drawing of the digestive system below is for illustration and is not drawn to scale.]