Keywords: prepuce, equine, prepuberal, colt
A frenulum joins the prepuce and penis on the ventral aspect of the penis in all domestic animals except for the equine species. Usually, the frenulum In most animals breaks down largely under the effect of androgens (perhaps attempts at erection as well) after puberty. In horses this is not the case. No frenulum is present at birth and within days of foaling, a colt is able to extend his penis completely.
During fetal development the penis is of course adherent to the prepuce, dividing itself from that structure as organogenesis proceeds.
In rare cases, exuberant adhesion between the prepuce and penis may actually occlude the preputial opening, even preventing urination. In one such case (see reference), gentle separation of internal lamina of the Prepuce and mild traction on the penis resolve the condition successfully
The images below show the penis and prepuce of a colt late in gestation. Note the tenuous connection between the penis and prepuce at this time. At the time of foaling, the penis will have separated completely from the prepuce.
Figure 1: Partial adhesion between penile and preputial mucosa (solid black arrow) in a newborn colt. The penis is being drawn to the right, the prepuce to the left. Image size: 3264 x 2448px
Reference
Canisso I.F. et al. 2020. Congenital phimosis causing preputial swelling in a newborn foal. Can Vet J .
61:247-250.
