Mare anal is the part of the reproductive tract containing the vulva, uterus and ovaries that produce eggs fertilized by semen during natural breeding, producing eggs to be fertilized by semen through natural breeding; additionally it serves as an endocrine gland producing estrogen and progesterone hormones for reproductive health.
The vulva is composed of two functional genital seals (labiae) that serve to provide a barrier between the external environment and uterine lumen. Their lips meet at dorsally at tightly angled dorsal commissure and ventral at more rounded ventral commissure. Between their lips is an area known as clitoral prepuce that often houses moist smegma from clitoral glans resulting from their intersection.
Prebreeding exams and evaluations of mares suspected of reproductive issues must include an examination of vulva and perineal conformation. Mares with poor vulvar confirmation tend to develop chronic infection of their vulvas by fecal material, leading to vulvitis, vaginitis, cervicitis and even death from chronic incontinence. Mares that experience difficult labor or abortion may experience bruises, hematomas and injuries to the anal tract that result in additional problems during birth/parturition that require special consideration when breeding them back out.
At the physiologic breeding season, mare behavior is controlled by secretions of Luteinizing Hormone (LH). LH production begins during behavioral estrus and peaks prior to ovulation (Figure 3). LH does not directly cause ovulation but instead triggers corpus luteum cells to produce an egg for fertilisation – typically during early luteal phase of their cycles.