Disorders of Sex Development in Donkeys

Disorders of sex development (DSDs) are congenital conditions where a donkey's chromosomal sex, gonadal sex, and physical sex characteristics do not line up in the expected way. Older terms like "hermaphroditism" may still appear in case reports, but DSD is the more accurate modern term. In veterinary medicine, these conditions can include animals with testes but female-appearing external genitalia, ovarian and testicular tissue in the same animal, or chromosome patterns that do not match the outward appearance.

In donkeys, DSDs appear to be uncommon, but they are documented. Published reports include donkeys with reproductive tract abnormalities and sex chromosome mosaicism linked to sterility. Much of what your vet uses to guide care comes from broader equine medicine, because horses and donkeys share many reproductive principles even though donkey-specific data are limited.

Some donkeys live comfortably with a DSD and are never intended for breeding. Others develop practical problems, such as infertility, repeated heat-like behavior, difficulty with breeding management, retained testicular tissue, or confusion about whether the animal can safely be housed with jennies or jacks. The goal is not to label the donkey. It is to understand the anatomy and make a safe, realistic care plan with your vet.

DSDs start during fetal development. Normal sexual development depends on several steps happening in sequence: chromosome pattern, activation of sex-determining genes, development of ovaries or testes, hormone production, and the body's response to those hormones. A change at any step can alter the final anatomy.

In veterinary species, DSDs may be linked to chromosome abnormalities, mosaicism, gene-level changes, failure of testes to descend, abnormal hormone production, or tissues that do not respond normally to sex hormones. Merck Veterinary Manual describes these conditions across domestic animals and notes that true hermaphroditism is rare, while male pseudohermaphroditism and other intersex states are more commonly recognized.

In donkeys specifically, published literature includes a jenny with reproductive tract abnormalities and a 62,XX/61,X mosaic chromosome pattern associated with sterility. That does not mean every donkey with infertility has a chromosome disorder, but it shows why your vet may recommend cytogenetic or genetic testing in unusual cases.

These conditions are congenital, meaning the donkey is born with them. They are not caused by routine handling, diet, or day-to-day management after birth. In most cases, prevention focuses more on breeding decisions and avoiding use of affected animals for reproduction than on anything a pet parent did or did not do.

Diagnosis starts with a careful history and physical exam. Your vet will ask about age, behavior, breeding history, fertility, prior castration records, and whether the donkey has ever shown heat cycles or jack-like behavior. A hands-on exam of the external genitalia and inguinal area can reveal ambiguous anatomy, a retained testicle, or scarring from prior surgery.

From there, your vet may recommend reproductive ultrasound, rectal palpation when appropriate, and bloodwork. Hormone testing can help determine whether functional testicular tissue is present. Depending on the case, your vet may also suggest anti-Müllerian hormone testing, testosterone testing, or stimulation testing used in equine reproductive workups.

If the anatomy is unclear or breeding decisions matter, advanced testing may include endoscopy, exploratory surgery, histopathology of removed tissue, and chromosome or genetic testing. Equine case reports show that karyotyping and molecular testing can be important when external appearance does not match internal reproductive structures.

Because donkey-specific reference data are limited, diagnosis often relies on a combination of donkey exam findings and equine reproductive medicine principles. It can take time to get a complete answer. In some cases, the final diagnosis is based on both imaging and laboratory confirmation after surgery.

Most DSDs cannot be prevented after conception because they develop before birth. There is no feed, supplement, or routine management step that reliably prevents them in an individual foal. That can be frustrating, but it is also important. These conditions are not caused by normal handling or everyday care.

The most practical prevention step is breeding management. Donkeys with confirmed or strongly suspected DSD, unexplained infertility linked to abnormal reproductive anatomy, or chromosome abnormalities generally should not be used for breeding unless your vet and a reproduction specialist advise otherwise. Careful recordkeeping matters too. If a foal is born with ambiguous genitalia, document the findings early and arrange a veterinary exam before making breeding or castration decisions.

Pre-purchase and pre-breeding reproductive exams can also help catch problems before they become costly or risky. If a young donkey has missing testicles, unusual genital anatomy, or behavior that does not match the recorded sex, ask your vet to investigate rather than assuming it will sort itself out with age.

For pet parents, prevention often means preventing complications rather than preventing the condition itself. Safe housing, avoiding accidental breeding, and timely veterinary evaluation can reduce stress, injury risk, and unnecessary procedures.