In last week’s blog, we discovered the practice of mare teasing. With the timing of each mare’s estrus cycle now determined using behavioral indicators, the Broodmare Farm Manager moves forward with internal examination via palpation and ultrasound.
Palpation is a procedure performed by a veterinarian who reaches into the rectum with their arm to feel the reproductive organs through the recto-vaginal wall. Ovarian size and consistency, follicle size and consistency, uterine tone, degree of cervical relaxation and pelvic structure are all inspected and the results noted.
We joined Dr. Thomas Riddle of Rood & Riddle as he performed rectal palpation on the barren and maiden mares. The breeding sheds will open around February 14th and, as these mares are not currently in foal, they can visit the stallion as soon as they are ready to be bred. The exams allow us to effectively communicate the likely day of ovulation, with two to three days advance notice, to the farm that manages the stallion. The close monitoring and communication will ensure the mare is covered when she has the greatest chance of conception.
A veterinarian uses palpation and ultrasound during different periods of the estrous cycle, both when the mare is in heat (estrus) and also the time period between heats (diestrus). While always looking at the same organs, there are major differences to be found. There is also a lot to learn about individual maiden mares, as it is the first time they have gone through this process.
To prepare a mare for palpation, she is positioned with her hind end pointing out of the stall into the breezeway. There is a handler at the mare’s head and another at her hindquarters. The handler at the hind end is responsible for holding the tail aside to create a clear path to the rectum.
Dr. Riddle begins palpation by putting on a disposable shoulder-length glove and applying a lubricant. He then reaches through the rectum, removing any feces that may be present. Once the rectal path is clear, Dr. Riddle proceeds with inspecting the ovaries, follicles, uterine tone, cervix and pelvis by feeling through the rectal wall. The grade of each is then verbalized to the Broodmare Manager regarding size, consistency, relaxation, and structure.
When a mare is in estrus the palpation exam will show that her ovaries have become larger and softer due to the development of follicles. Follicles are fluid-filled vesicles that contain a developing egg.
In the past, palpation was the only examination method available, but with the introduction of ultrasound technology, veterinarians are able to not only feel but also see. The rectal ultrasound examination follows rectal palpation, allowing Dr. Riddle to confirm the palpation exam. A small ultrasound wand is held in Dr. Riddle’s hand within the rectum and the image transmitted to a small monitor. He accurately measures the size of ovaries and follicles and determines the presence of uterine edema, fluid, and cysts.
Presence of fluid in the uterus, typical to some degree during ovulation, is recorded. During ultrasound of a mare in diestrus, the lack of fluid allows the veterinarian to see and document the location of uterine cysts, referred to as a “cyst map”. In most cases, cysts do not affect the mare or her ability to carry and deliver a foal, but monitoring is important. The appearance of a cyst on an ultrasound is identical to that of a very early pregnancy. Without the cyst map, a false confirmed pregnancy could occur when the mare is examined post-breeding.
Cervical relaxation is graded from one to four. A ‘one’ cervix is tight and firmly closed; a ‘four’ cervix is open and relaxed. During ovulation, the open cervix provides a pathway for the sperm to reach the follicle. When a mare is not ovulating or is pregnant, the cervix will be closed.
During palpation, the veterinarian will determine if the cervix is relaxed enough to be examined with a speculum (a very long, thin tube). As the speculum must be used via vaginal exam, the tail is wrapped and the outer part of the vagina is cleaned using an iodine and soap mixture. It is important to keep the vaginal area clean so that no dirt or debris enters.
Dr. Riddle passes a culture swab, via the speculum, through the cervix, and into the uterus. This swab will collect a sample from the mucosal lining of the uterus. The swab is removed carefully and placed in a tube of culture media and taken to the laboratory and set up for culture, which will identify any growth of bacteria. No growth of bacteria is known as a ‘Clean Culture’, and a certificate stating such must be provided when the mare visits the breeding shed. If bacterial growth is identified, the mare will be treated appropriately and reexamined until the infection is abated.
While one may imagine these exams to be uncomfortable, mares generally have no issue with them. Important information about the mare is discovered during these exams and allows the Stonestreet team to provide the best possible individualized care.