Mares are the female offspring of horses and donkeys. Horses possess 64 chromosomes while donkeys only 62, leading them to require neutering through gelding; during this process, anal glands are removed as well as parts of the reproductive tract such as the clitoral hood that suckers sperm into the uterus as well as any potential vulvas that are removed during rectum opening to remove any potential threats to fertility and sexual function.
As parturition approaches in some horses, third degree rectovestibular lacerations is not uncommon. These lesions become heavily infected with feces and result in significant amounts of prolapsed rectum tissue being unsalvageable; their prognosis resembles that of hernias in humans.
A mare’s genitalia should be assessed for conformation and muscular tone. The vulva acts as the first physical barrier against pathogenic organisms entering her reproductive tract; for optimal perineal conformation it should sit nearly vertical with at least 70% ventral to pelvic brim; horizontally sloping dorsally due to recession of anus or poor muscular tone in labia may predispose to pneumovagina infections that are difficult to treat.
Transrectal palpation is another key exam, where a veterinarian inserts their hand into a mare’s rectum and feels its vulvae to assess whether there is a functional cervix. This procedure should take place 16-19 days after being exposed to either a stallion or artificial insemination, or it could potentially occur sooner unless pregnancy can be confirmed through other means.