Is Sheath Cleaning Necessary?

You’ve been told that regularly cleaning your gelding’s sheath is important for his health and hygiene, but it’s no one’s favorite job, and many horses object to it. Is it really necessary? Maybe not. The goal of cleaning is to lower any risk of irritation and infection by removing the waxy secretions, called smegma, that collect in this sensitive region. But frequent cleaning, it turns out, actually fosters an increase in bacteria and gunky secretions in the sheath.

A recent study indicates that routine sheath cleaning may not be needed. | © Paula Da Silva/

Fresh evidence for this comes from a research project carried out at Delaware Valley College in Pennsylvania. Mariah Beaver, a senior equine science student at the college, assessed the effects of sheath cleaning on 19 geldings. The horses were divided into four groups: control (not cleaned), cleaned with a water rinse, cleaned with a commercial sheath-cleaning product and cleaned with baby shampoo. Beaver swabbed the horses’ sheaths before and after cleaning and cultured the samples in the lab, so that bacterial colonies could be counted. She repeated the cleaning and testing three times, with three weeks between cleanings. Here’s what she found:

· Samples taken after cleaning showed significantly more bacterial growth—from 10 to 100 times more—than samples taken before. (The bacteria identified did not pose a direct threat to the horses, but some types have been linked to urinary tract infections.)

· The horses that were washed with the commercial product had the greatest increase in bacterial numbers after cleaning. Those washed with plain water had the least.

·The buildup of smegma returned to pre-washing levels within the three weeks between cleanings. “Cleaning the sheath can cause a response from the body increasing smegma build-up,” Beaver reports.

· There were more bacteria both before and after the second and third cleanings than before and after the first cleaning.

In short, cleaning set the stage for bacterial growth. Why? Beaver says that proteins in smegma have antimicrobial properties. She confirmed this in the lab by isolating the proteins and performing an assay. “I placed protein in broth with various bacteria, including bacteria I isolated from the sheath cleanings,” she explains. The proteins inhibited bacterial growth. Delaware Valley faculty members Angelo Telatin and Cynthia Keler assisted in the research, which was presented last summer at the International Equitation Science conference in Denmark.

While geldings (and stallions) may not need routine cleaning, it’s still important to check the sheath and penis regularly for lesions and other trouble signs. A swollen sheath or difficulty in peeing—the horse doesn’t drop to pee, starts and stops, or sprays or dibbles—suggests that something’s amiss. The horse may need to be cleaned or he may have a condition that needs other treatment. Your veterinarian can help sort out the signs. 

This article originally appeared in the November 2014 issue of Practical Horseman.

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