I’m going to talk a little about cleaning the sheath of stallions or geldings. I don’t relish discussing this topic, but I keep coming across people who believe it is an important part of horse husbandry. I don’t know if it’s worth noting that in my experience it is always women who insist on cleaning the sheaths of their horses – never men. But I will leave it the Freudians to explain that one.

Over the years, I have been told many times what an uncaring horse owner I am for not cleaning the sheaths of my geldings. So after inadvertently coming across a video on the subject I finally felt compelled to explain.

I have always questioned the need to clean the sheath. I have been told several reasons why it is important, but most of them seem to be myths and not based on real facts. If a person were to believe the reasons why sheaths need to be cleaned regularly, it can only leave a person thinking it is a miracle that wild horses were ever able to reproduce.

Most people who believe in the importance of cleaning sheaths seem to have fallen for the idea that an unclean penis looks dirty therefore it is dirty. In particular, the build-up of oily substances that continually secrete from the penis leads to a build up of smegma  - sometimes dry and sometimes oily. It looks bad and disgusting, but it is perfectly normal and even healthy. 

The amount of smegma produced varies from horse to horse. Horses with white penises tend to produce more smegma than those with black ones, however, both are normal. It is very rare that a horse produces too much smegma and needs to be managed by cleaning.

There is a misconception that smegma harbours unhealthy bacteria and needs to be removed regularly, but in fact, smegma protects the penis from bacterial infection. Cleaning the penis of smegma makes horses more susceptible to infection.

Some breeders also believe that cleaning stallions lowers the risk of introducing infection to a mare and also increases the rate of fecundity. However, as I have just said smegma is protective against infection (it contains anti-microbial agents shown to inhibit bacterial growth) and it has been demonstrated in a study in Pennsylvania that the bacterial population on the surface of a penis is greater days after cleaning than before cleaning. Some of those species of bacterium have been linked in other studies to uterine tract infections. It can take up to 3 weeks for the normal bacterial population to return to normal after cleaning.

Furthermore, it has been recorded that stallions in the wild reach conception rates of up to 85 percent, which compares favourably with the conception rates of many domestic stallions (70+ percent). That is not proof that unwashed sheaths lead to better productive outcomes, but it does suggest that leaving them unwashed does not diminish the rate of conception.

Another reason people sometimes feel compelled to clean the sheath is to remove a small accumulation of smegma from the end of the penis (urethral fossa) called a plug or bean. It is thought by some that this plug hinders a horse’s ability to urinate. The problem is typified by a ‘camped-out’ stance and hunched back while trying to urinate. However, it has been shown that the build up of smegma (plug) is no match for the force of the stream of urine and is easily ejected during urination when the plug grows too big. It is more likely that the posture of hunching the back is an indication of other problems such as back pain (caused by the camped-out posture) or ulcers.

Finally, occasionally a sheath can appear enlarged or swollen. Many people take this as a sign that the sheath needs cleaning. But the swelling is usually simply a build up of fluid during confinement due to the sheath being a low point on the body and where fluid drains towards – no different to how legs swell because gravity sends fluid in that direction. Most times the edema in the sheath is fixed by exercising the horse.

But are there times when the sheath should be cleaned? Yes.

I had a horse that had a squamous cell carcinoma on his penis and flies laid maggots in the wall of the tumour. It required that I washed his penis every day for about 10 days before the wound healed and didn’t need care anymore. 

Sometimes a penis can have a small cut that requires regular cleaning to avoid infection. However, once the cut has healed it is not necessary to clean the penis anymore.

If you have a horse that needs their sheath cleaned for medical reasons, there are a couple of rules to keep in mind. 

Firstly, never try to force a horse to drop its penis. If your horse is reluctant to drop its penis, it is better to sedate the horse (which will cause it to drop naturally) than try to physically force it out of hiding. It is a sensitive organ and needs to be handled gently.

Secondly, when cleaning the area always be gentle – do not scrub. Most of the smegma will flake or peel off easily and often you don’t even need water. Never use chemicals or harsh detergents and be careful not to break the skin.

I know some people will think this article is rubbish and not cleaning a horse’s sheath is a sign of an uncaring and negligent owner. But the bottom line is that a hell of a lot of gelding and stallions (both domestic and wild) get by and live long lives with never having had their sheaths cleaned. I know this because I have owned such horses..