There are a few areas on the body that provide important information regarding the state of a horse's circulatory health. These areas include the gums, the pink membrane inside the nostril, the whites of the eyes, and the pink inner vulvar membranes of mares. The simple act of evaluating the color of your horse's gums is actually a very important skill.

A yellow cast to the mucous membranes of the gums or the whites of the eyes (sclera) is associated with a variety of diseases involving destruction of red blood cells and liver disease. Horses suffering from these disease processes also tend to exhibit other signs of illness.

Taken alone with no other signs of illness or abnormalities, a pale yellow cast to the gums or sclera may not be cause for worry. Horses that do not eat for a period of time develop yellow tinged gums. Horses eating certain plants, especially those on pasture, can develop yellow gums from the accumulation of plant pigments.