Herd stud teasing a "receptive" (tail position) mare..

This is a yearling colt teasing a heat mare with a classic nip on her elbow.  She begins to empty her bladder, which is one of the prime results of teasing. A mare with a full bladder, will urinate when the studs penis enters her and puts pressure on her bladder.  New studs seem very perplexed as the urine surrounds his shaft and exits from the mare. Usually terminates the mating.