Sheath-cleaning enthusiasts present a sensible argument for addressing the hygiene of their male horse. Yet a new study presented in Denmark has shown routine/regular cleaning of a horse’s sheath to not only be unnecessary, but disruptive to the healthy populations of “friendly” micrograms that call this location “home.”
The sheath surrounding the penis, also called the prepuce, is a double layer of sliding skin that covers the drawn-up penis. The internal fold of skin contains numerous sebaceous glands that secrete lubricating oils. These secretions, together with sloughing skin cells and dirt, form a grey to black, thick, waxy and/or greasy and/or gummy material called smegma which collects in the folds of the sheath. These secretions can vary in nature, sometimes appearing as yellowish wax-like deposits or dry, hard flakes.
When a stallion or gelding extends or ‘lets down’ his penis, one can readily see the accumulation of smegma. This material is continually secreted and its purpose is to lubricate and protect the penis. Smegma is normal and individual horses can produce different amounts, colours, and consistencies of it.
Smegma may vary in quantity and type, but all of it is normal and in fact the study determined smegma to serve a physiological advantage providing a natural protective covering. Proteins from the smegma were found to have important antibacterial properties. Under study, not only did bacterial numbers increase following sheath cleaning, but surprisingly it was discovered that smegma production rebounded within three weeks following cleaning.
Whilst geldings and stallions may not need routine sheath cleaning, it’s still essential husbandry practice to examine the sheath and penis regularly for lesions and other signs of trouble. Usually in the day-to-day activities around the horse, opportunities arise for a visual inspection. Any difficulty or discomfort in urinating such as an interrupted urine stream, spraying or dribbling of urine, reluctance to drop the penis while urinating or unusual posturing and/or behaviour while urinating, suggest something is amiss.
It is not uncommon for older male horses with a “bean” to exhibit such signs of urinary discomfort. A “bean” is a buildup of smegma, dirt, and the mineral salts from urine which form a hardened clay-like ball of debris at the end of the penis.
Beans can vary in size from a pea to the size of a kidney bean. They accumulate in the urethral diverticulum which is a small pocket or “cul-de-sac” near the urethra. Depending on the size and makeup of the bean it can cause considerable irritation as the horse attempts to pass urine and cannot do so comfortably. Removal of the troublesome “bean” brings noticeable relief to affected horses. Veterinarians will generally examine a horse’s sheath or check for a “bean” during tranquilization for routine procedures such as dentistry. Tranquilizers cause the penis to relax and extend, making evaluation and necessary procedures much easier.
A “dirty sheath” is oftentimes blamed for swelling of the sheath. This is rarely the case though. Since the sheath is located on the underside of the horse, it is a natural low point where fluid accumulates by the forces of gravity.
A swollen sheath is more commonly a symptom indicating low protein levels in the blood, poor circulation, parasite infestation, or liver disease. Horses that are overweight or lack movement tend to accumulate “swelling” in the prepuce. The prepuce may mistakenly appear swollen when it is fat laden. During the winter, horses confined to small feed yards lack the movement necessary to support optimum circulation and can potentially develop preputial swelling. Exercise resolves the unwanted swelling.
Although mares do not get smegma per se by definition, they can accumulate a smegma-type material between their mammary glands. Mares with an uncomfortable buildup of thick plaques may tail rub, fence sit, and gait abnormally. Simply resolving the buildup when indicated can have surprisingly gratifying results in the mare’s behaviour.