One of the many unglamerous tasks associated with horse ownership is genital hygiene. Both boys and girls get...er...gunky as their natural secretions mix with dirt and stick to the surrounding skin. In the wild I assume that stallions stay clean by breeding and that mares stay clean by birthing and nursing, but domestic animals need some (ideally semiannual) assistance.
A few days ago I saw Raven enthusiastically rubbing her rump against the fence, which is often a sign of uncomfortable girl parts (she is up-to-date on her worming). Mares get dirtiest between their udders, but fluid from the vulva also pools and sticks between their hind legs. When I last cleaned Raven in May she was VERY unreceptive and I was forced to do a cursory job (while dodging blows). Today was a different story -- she looked totally content and relaxed throughout the half hour of fussing and scrubbing and picking and rinsing required to get her squeaky clean. Another testament to how much she is starting to trust me.
Tonka, on the other hand, would probably trust anyone to clean his sheath because he is a giant horn dog. He looked a bit uncomfortable when I removed a small "bean" (a hard ball of dirt and smegma that collects in the tip of the urethra), but otherwise he made a lot of sexy faces and some silly grunting noises. His eyes did bug out a little when I put the cold hose right up there to give him a final rinse. A good job to get done on a sunny day.