When evaluating the overall health of a horse, on first impression we focus on the obvious–the bloom of the hair coat, the horse’s attitude, his posture and stance. Beneath this outer appearance, we can find another useful clue about the health of the internal workings of a horse: The mucous membranes.

Mucous membranes are tissues that line body cavities, and they are visible wherever skin interfaces with a body opening, such as the gums, the vulva, the prepuce and penis, inside the nostrils, and the conjunctival sac of the eye. These membranes secrete viscous mucus that keeps them moist and protected, and they are also well-supplied with blood to give us useful information about the circulatory status of the horse.

Mucous Membrane Color

Mucous membranes give  an impression about the efficiency of the heart as a pump and the capacity of vessels to carry the blood circulation to the periphery. When an adequate supply of oxygenated blood is carried to all areas of the body, the color of the gums should be similar to the pink hue that you see beneath your fingernails. Any departure from this pink might mirror an internal change.

A pale color indicates a reduction of red blood cells and/or oxygen in the peripheral circulation. This could result from blood loss, dehydration, anemia (a deficiency of red blood cells), or hemoglobin related to blood loss (acute or persistent), or chronic bacterial, or parasitic infection. Chronic blood loss occurs with leakage from the gastrointestinal tract, such as with bleeding gastric ulcers or with excretion through an inflamed urinary tract. Tissue necrosis related to cancer of internal