Disorders of Sex Development in Pigs: Genetic and Reproductive Implications

Disorders of sex development, often shortened to DSD, are congenital conditions present from birth. In these pigs, chromosomal sex, gonadal sex, and visible reproductive anatomy do not develop in the usual matching pattern. Older terms like intersex or hermaphroditism may still appear in research papers, but DSD is the more accurate modern term.

In pigs, one of the best-described forms is 38,XX DSD, where a pig has a female chromosome pattern but develops some male reproductive features. Research in swine has shown that affected pigs may have ovotestes, mixed internal reproductive structures, ambiguous external genitalia, and abnormal gonadal tissue with poor or absent germ cell development. That means fertility is often reduced or absent, although anatomy can vary a lot from one pig to another.

For pet parents, the biggest concerns are usually practical ones: whether the pig can urinate normally, whether there is pain or infection risk, and whether retained or abnormal gonadal tissue should be removed. For breeding herds, DSD also matters because it can affect fertility, culling decisions, and genetic selection. Your vet can help sort out which concerns matter most for your individual pig.

DSD in pigs is usually caused by abnormal sex determination or differentiation during fetal development. In simple terms, the genes and hormones that guide development of ovaries, testes, and the reproductive tract do not follow the usual pathway. In swine, the most commonly discussed form in the research literature is SRY-negative 38,XX sex reversal, where pigs without the usual Y-chromosome sex-determining signal still develop testicular or mixed gonadal tissue.

Studies in pigs have linked some cases to changes involving genes that influence testis development, including pathways around SOX9 and other regulatory regions. Not every case has a single clear mutation, and some pigs may have chimerism or mosaicism instead of one straightforward inherited pattern. That is one reason your vet may suggest chromosome testing or referral to a diagnostic laboratory if breeding decisions are involved.

It is also important not to confuse DSD with other reproductive problems that can look similar from the outside. For example, estrogenic mycotoxins such as zearalenone can cause vulvar enlargement and reproductive changes in pigs, but that is a toxin exposure problem, not a congenital DSD. Your vet will use history, exam findings, and testing to separate these possibilities.

Diagnosis starts with a careful physical exam and a detailed history. Your vet will look at the external genitalia, check for palpable gonads, ask about urination, heat cycles, breeding history, and growth, and consider whether the findings fit a congenital condition or another reproductive disorder.

From there, testing is often layered. Ultrasound can help identify internal reproductive structures such as uterine horns, retained testes, or mixed gonadal tissue. Bloodwork may be used to assess overall health before anesthesia or surgery, and hormone testing may be helpful in selected cases. If the anatomy is unclear, advanced imaging or exploratory surgery may be the most practical way to define what structures are present.

For pigs with suspected DSD, the most definitive workup may include karyotyping, PCR for SRY, or other genetic testing, plus histopathology of any removed gonadal tissue. That information helps your vet discuss fertility expectations, cancer or infection risk from retained tissue, and whether related pigs should be excluded from breeding programs.

Because DSD is usually congenital and genetic or developmental, there is no guaranteed way to prevent every case in an individual pig. Prevention is mostly about breeding management rather than home care. If a pig is diagnosed with DSD, your vet may advise against breeding that animal and may also recommend reviewing related animals in the line, especially if similar reproductive abnormalities have appeared before.

For breeders, good records matter. Track litter history, fertility outcomes, ambiguous genital findings, and any pigs removed from breeding for reproductive reasons. When possible, work with your vet and herd advisors to avoid repeating pairings linked to suspected inherited defects.

It also helps to reduce confusion with look-alike conditions. Feed quality control is important because estrogenic mycotoxins such as zearalenone can cause vulvar enlargement and reproductive changes that mimic congenital problems. If a young pig develops sudden vulvar swelling or herd-wide reproductive signs, your vet may want to investigate feed exposure as well as congenital causes.