Colic and the equine microbiome: Dysbiois happens

Colic is unpredictable and can affect any horse at any time. The term “colic” means abdominal pain, and it also broadly refers to a variety of conditions that causes abdominal pain. Recently, studies have shown changes in the composition of the equine gut microbiome during and following a colic episode. Researchers from Chile sought to identify the relationship between the changes in the microbiome and colic in equines and to determine if the microbiome changes are causes or effects.

Although treatment and surgical options are available, colic is one of the major causes of death in equines. Due to the high mortality rate, researchers were keen on identifying risk factors for colic in equines to reduce its prevalence. In 2019, a study discovered the 2 most common risk factors: a decrease in water intake and/or a change in the hay or concentrate (dietary supplement) consumption.

The gut microbiome serves many functions. It assists and promotes digestion, facilitates the fermentation of indigestible carbohydrates, stimulates the immune system, and creates a barrier against toxins. The microbiome is home to trillions of microorganisms: bacteria, fungi, viruses, and parasites. Some microbes are beneficial, but others are potentially harmful or pathogenic. In a healthy gut, these opposing microorganisms coexist in a delicate balance. Dysbiosis, disruption of the microbiome balance, can arise from various causes such as confinement, antibiotics, fasting, stress, age, and diets high in concentrate. Dysbiosis is also associated with some diseases and syndromes, like irritable bowel syndrome (IBS), due to the loss of certain necessary bacteria that keep the proper balance. The microbe diversity in the gut microbiome decreases in equines with colic.

Sudden changes in the diet can cause the alteration of fermentation patterns. Due to the fermentation, bacteria such as Lactobacillus and Streptococcus cause lactic acid and gas to build. This accumulation causes a drop in the pH of the hindgut and subsequently results in the loss of certain bacteria. Pregnant mares are most at risk for colic because of the changes in their diet before, during, and after pregnancy.

Researchers have determined many factors that can cause dysbiosis and put equines at risk for developing a colic episode. They have also observed the difference in the composition of the microbiome in horses with colic and healthy horses. More research is needed to determine the relationship between the alterations in the microbiome and colic in equines.

Bean, PharmD, is entering a veterinary pharmacy residency in Wisconsin

References

Lara F, Castro R, Thomson P. Changes in the gut microbiome and colic in horses: Are they causes or consequences?. Open Vet J. 2022;12(2):242-249. doi:10.5455/OVJ.2022.v12.i2.12