What a week! I am exhausted just from watching the clinic staff in recent days – Springhill Equine has been in full swing for breeding season these past two weeks! In honor of that, I felt it was time we continued our discussion on horse breeding. This week, I would like to segue into the male side – basics of management of stallions and geldings. A stallion is a male horse that has not been castrated and is sexually mature (vs. a colt, which is not mature). A gelding is a stallion or colt that has been castrated. Sexual maturity is reached at about 4 years of age, but many colts will exhibit stallion-like behavior and sexual activity as early as 8 months of age. They should be separated from females when this is observed.

Castration, or removal of the testes and associated structures, is commonly performed on horses, as stallions can be tricky and difficult to handle and manage. Stallions are often housed in facilities separate from mares so no accidental breedings occur. They must be handled with a firm but cautious hand. With all of this said, there are many stallions out there who are considered docile and easily managed.  Geldings that are castrated before significant stallion behaviors develop, on the other hand, make wonderful companion and riding animals, and are generally more docile. If a stallion is castrated later in life (eg, more than 2 years of age), stallion-like and/or aggressive behaviors may persist post-castration. It is not recommended for the beginner horse-person to own a stallion – usually males are only kept stallions (or ‘intact’) in situations where they will be specifically used for breeding purposes. Some are left intact until physical characteristics develop (eg, larger size, crested neck), and are then castrated. Thoroughbred racehorses are often kept as stallions so they have the potential for a breeding career if their racing career proves successful.

Let’s talk more about the specifics of the male horse reproductive tract. As with any mammal, both stallions and geldings have a penis as their external genitalia. Unlike humans, however, the male horse’s penis at rest is telescoped within itself, and is housed inside the body during the majority of the time. He will externalize the penis (as one would extend a telescope) during times of sexual arousal, for urination, or during sedation/relaxation. There can be medical issues that result in the horse becoming unable to retract the penis, and can become a major problem if left externally for an extended period of time (just like they say on the Viagra commercials – 4 hours is too long!). Tumors and other skin conditions of the penis are relatively common in horses, so regular cleaning of the dirt and skin oils (termed ‘smegma’) from the penis and sheath is important. The vets here at Springhill Equine clean any male horse who is sedated for a dental float, and check them thoroughly for any signs of cancer or other abnormalities.

Stallions also have a pair of testes housed externally in the scrotum. Veterinarians are aware of several conditions that can arise with the scrotum and testes – including infections, tumors, testicular torsions (a medical emergency that presents often as severe and sudden colic), and scrotal hernias. The testes is the assembly factory for sperm, while the next-in-line epididymis is responsible for sperm maturation – eg. packaging and storage. On ejaculation, the sperm leave the tail end of the epididymis, where they are waiting in storage, and travel up toward the pelvis along the ductus deferens (analogous to the vas deferens in humans) until they dump into the urethra (also the exit for the urinary tract) at about the level of the anus. Fluid is added from three different glands (bulbourethral glands, seminal vesicles, and prostate) to help the sperm along their journey. They travel along the urethra through several feet of penile tissue (whose base is just below the anus internally) before exiting with the goal of seeking an egg. In our next blog, we will discuss the various routes a sperm can take to reach that egg – with the stallion actually breeding a mare, or via artificial insemination (A.I.) with fresh, cooled, or frozen semen.

Thanks for stopping by to read my blog this week, maybe next time I could see you in person at the clinic (for some pets)! Keep emailing if you have any specific questions you would like me to cover in my blog (or in the newsletter, for that matter!)! May your litter box be clean, and your food bowl full!


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