By Ben Espy, DVM, DACT
Question: I just bought my first horse—a gelding. My fellow barn mates tell me that I need to clean his sheath several times a year. Do I really need to do that, and, if so, how?
A. Contrary to popular belief, cleaning a horse’s penis and the sheath containing it (the prepuce) is rarely necessary. In fact, the aggressive cleaning methods promoted by many well-meaning horsepeople often do more harm than good. Here are some myths commonly used to justify this practice:
Myth #1: Accumulation on the penis is dirty and unhygienic. This is a typical anthropomorphic assumption that male horses have the same hygienic needs as male humans. As with most things we do to horses to make them align better with our lifestyles, we’d be better off letting horses be horses. When a stallion or gelding extends or “lets down” his penis, the accumulation you see on it is smegma, not dirt. This material is continually -secreted from the penis for a very specific purpose: It provides lubrication and a protective covering for the penis.
Some horses produce dry, flaky smegma, while others produce moist, goopy smegma. Both are perfectly normal. The amount produced varies widely among individuals. For example, horses with white pigmentation on their penises seem to produce more smegma than horses with dark penises. Excessive smegma accumulation is extremely rare and usually associated with skin conditions or lesions, like herpesvirus or squamous cell carcinoma—a common tumor found on the penis—that need to be diagnosed by your veterinarian.
Myth #2: All male horses require routine sheath cleaning. The best proof that sheath cleaning is completely unnecessary is the reproductive health of stallions observed in the wild. These horses, who obviously have never had their sheaths cleaned, have documented conception rates approaching 85 percent. Domestic stallions, on the other hand, who do frequently have their sheaths cleaned—sometimes as often as three to four times a day—often average only a 70 percent conception rate.
Some instances in which sheath cleaning may be medically recommended are when a horse has suffered a laceration in the area, has undergone surgery to remove a cancerous growth, has a skin condition from equine herpesvirus or has squamous cell carcinoma.
Myth #3: Swelling in the sheath and tail rubbing are signs that a horse’s sheath needs cleaning. When a sheath swells, it has nothing to do with the accumulation of smegma inside it. -Because of its location on the underside of the horse, it is simply a natural low point where excess fluid is drawn by the force of gravity. For example, an older horse with low protein levels in his blood or liver disease may experience fluid buildup, called edema or pitting edema—swelling that holds a depression when you press into it with your thumb—in the sheath area without exhibiting any other clinical signs. In such cases, the swelling likely will disappear if the horse is turned out or exercised, just as it would from the legs of a horse who stocks up when stalled for long periods of time.
Another common cause of sheath swelling is parasites. Parasites also make horses’ tails itchy. So if you notice your horse rubbing his tail and he has a swollen sheath, the latter condition isn’t causing the former. Both can be cured by deworming with an ivermectin-containing product.
Myth #4: An unusually large smegma “bean” can block a horse’s urethra. Smegma can accumulate in the depression at the end of the penis, called the urethral fossa. Commonly known as the “bean,” this smegma plug can vary from about the size of a small eraser to a lima bean. When male horses stand “camped out”—with their hind legs stretched behind them and their backs hunched in an uncomfortable-looking stance—some people worry that they’re having trouble urinating. But the force of a horse’s urine stream is far too strong to be inhibited by any amount of smegma. In fact, the “camped-out” stance is usually a sign of abdominal pain caused, for example, by ulcers or colic.
Not only is sheath cleaning unnecessary, it can often be harmful. The traditional method of poking a hose up into the sheath and scrubbing it and the penis with sponges and antibacterial soap removes the natural protective covering and healthy bacteria population, potentially causing microabrasions and sores.
If you feel absolutely compelled to clean your horse’s penis for cosmetic reasons before a show, follow a quick, efficient, soap-free procedure. To -encourage him to let down for cleaning, try bathing him on a warm, sunny day. Then stand by his front legs to avoid getting stepped on if he sidesteps during the process. Wearing disposable gloves, gently grasp the end of his penis with one hand and run the other hand up the shaft, knocking off the smegma. You should be able to clean the penis adequately this way without using water. If necessary, though, you can run a small stream of warm water over the penis—but avoid scrubbing with towels or sponges. Then pat the penis dry with paper towels.
If your horse doesn’t relax enough to let down or refuses to stand still for the procedure, don’t resort to more forceful restraints, such as a twitch. This will just stimulate his fear mechanism, making it harder to clean his sheath in the future. Instead, ask your veterinarian to sedate him and perform the cleaning for you.
Expect whatever cleaning you do to be short-lived. Normal smegma production will restore the accumulation to your horse’s regular level within about a week.
A specialist in equine reproduction and infertility, Dr. Benjamin Espy has practiced veterinary medicine in Texas and Kentucky and is board certified in equine reproduction and licensed to practice acupuncture. He recently served on the AAEP Board of Directors and the Board of Directors for the American College of Theriogenology (www.theriogenology.org). Dr. Espy is also the liaison for the Texas Equine Veterinary Association and is a veterinarian for the Professional Rodeo Cowboys Association during the San Antonio Stock Show and Rodeo.
Reprinted with permission from the Practical Horseman magazine.
Reviewed by original author in 2016.