Working under the black coat
A young Friesian carries a dense, uniformly black coat, a long tail and heavy feathering early, and that combination hides outlines that are obvious on a fine-coated foal. Sexing one is therefore a hands-on check, not a look from the gate. The anatomy is the same as any foal's: lift the tail and look first. A filly has two openings under the tail, the anus and, immediately below it, the vulva shown as a short vertical slit. A colt has the anus only, because his genitalia sit forward on the belly. In the dark hair of a Friesian, run a fingertip over the area to confirm what the light may not show you clearly.
The colt: find the sheath, forget the testicles
On a young Friesian colt, the dependable sign is the sheath midway along the underside of the belly, a fold of skin on the centre line that you can feel even when the coat hides it. New owners often go looking for testicles and, finding none obvious, record the foal as a filly, but in a young colt the testicles frequently have not descended yet and on a well-covered Friesian they are hard to feel even when present. Absence of testicles is not evidence of a filly. Sheath on the belly plus a single opening under the tail is evidence of a colt, and it is all the evidence you need at this age.
The filly: two confirmations in the dark
A young Friesian filly gives you two separate confirmations, and in a black, hairy foal it is worth taking both. The first is the vulva directly under the tail, felt as a distinct opening beneath the anus once you part the tail hair. The second is the pair of small teats between her hind legs, where the udder will one day be; on a Friesian these sit within thicker belly hair than a light breed carries, so feel for them with a flat hand rather than expecting to spot them. Friesian fillies are often just as tall, arched-necked and imposing as the colts, so never let the foal's presence or prettiness argue you out of what your hands have told you.
Setting up the check with the mare
Friesian mares are devoted and can be possessive with a new foal, so have a helper hold the mare where the foal can see her, and position the foal alongside her rather than separated in an open space. Work from the side, one hand resting on the hindquarter, lift the thick tail once and look and feel in the same moment, then let the foal go back to nursing. Keep the session brief and fold it into early handling: touching the belly, legs and tail area calmly now is the foundation for every later examination this horse will ever have, and a rushed grab that startles the foal teaches exactly the wrong lesson.
Confirm, record and keep it consistent
Have the vet confirm the Friesian foal's sex during its first examination, and record the result that day beside its birth details and any markings, noting that with an all-black breed the written details carry more of the identification work than colour notes do for other breeds. Studbook paperwork, insurance, future sale or loan documents and your own youngstock management all copy this single fact, so the minute spent confirming it protects years of records. KinsLe's Pet Pass holds a young Friesian's identity and owner contact details on its verified ID card, keeping its recorded sex attached to the foal from its first week onward.