Problems with mare's reproductive ability might be detected in routine breeding soundness examination

THIS TIME of year, we are concerned with the mare's uterus as it relates to getting a foal to grow inside it. The mare's external genitalia often are ignored, but things can go wrong there to prevent pregnancy from taking place. The external genitalia of the mare consist of the vulva, clitoris, vagina, and cervix. Some of these may seem to be internal, but you do not get internal until you pass through the cervix.

Several conditions related to these areas of the mare's anatomy might be detected during a routine breeding soundness examination, which should be done prior to breeding. A diligent search for problems should be made following a difficult foaling (dystocia).

Vulva

The purpose of the vulva is to form a protective barrier to the vagina and cervix. The constrictor muscles of the vulva close the vulvar lips, forming a shield against the outside world. The vulvar lips should meet evenly with a cranial to caudal slope of no more than 10¡. If the angle is greater, the vulva should be sutured in what is known as a Caslick's procedure.

Perineal lacerations occur as the result of dystocia. Mild lacerations need no attention, but more severe ones should be corrected by surgery. Equine coital exanthema is a sexually transmitted disease caused by equine herpesvirus-3, but it does not affect fertility. It is manifested by the appearance of papules, pustules, and erosions of the vulvar mucosa and perineum. The lesions heal spontaneously and no treatment, other than three weeks of sexual rest, is necessary. There is no vaccine for equine herpesvirus-3.

Dourine has been wiped out in North America and western Europe, but still occurs in eastern Europe, Asia, Africa, and Latin America. Clinical signs develop slowly and include fever, systemic illness, genital edema, and a mucopurulent (combination of mucus and pus) vaginal discharge. There is a high mortality rate.

Clitoris

The clitoris is located just inside the lower end of the vulva. Not much goes wrong here, but the clitoral sinuses (small pockets in the clitoris) are a site favored by the bacterium that causes contagious equine metritis, the disease du jour in the late 1970s. The disease causes a heavy purulent vaginal discharge as well as a uterine infection. The recommendation at the time was to remove the clitoris of infected mares.

Vagina

The lumen of the vagina is collapsed under normal conditions and forms a protective barrier.

Pneumovagina is the term for a vagina filled with air (wind sucking). This often is the result of poor vulvar and perineal conformation, and a mare thus affected often has a history of recurrent endometritis and subfertility. Suturing the vulva is a simple corrective measure in most cases.

Urovagina (urine pooling). The normal mare's vagina is slightly elevated cranially, but if the slope changes so that the cranial aspect is lowered, the urethral opening is pulled forward. When this happens, all the urine cannot be voided and there is a backflush that pools in the anterior of the vagina. If the cervix happens to be open (when the mare is in season), urine will enter the uterus, causing irritation and inflammation. If urine is present when the mare is bred, the urine is toxic to spermatozoa.

Several things predispose a mare to urovagina, including poor vulvar and perineal conformation, pneumovagina, and old age.

Urovagina is more likely to occur when a mare is in season because the reproductive tract is relaxed and edematous, which can cause the vagina to tip forward. The condition is easily diagnosed by speculum examination. Several surgical procedures can be performed to correct the situation, but a complete breeding soundness examination, including a uterine biopsy, should be done before performing surgery.

Vaginitis is uncommon in mares, but may occur following dystocia, urovagina, pneumovagina, uterine infection, or rectovaginal fistulas (a tear between the vagina and the rectum). Necrotic vaginitis (in which the vaginal tissue dies) may develop secondarily to traumatic lesions.

There is a mucopurulent vaginal discharge and edema and hyperemia of the vaginal membranes. Culture of the exudates, or discharge, will show the causative organism. Mild cases will recover spontaneously, but more severe cases require vaginal douches of antibiotics. The prognosis is fair to good. Necrotic vaginitis must be treated with systemic antibiotics and the prognosis is poor. The mare could end up with vaginal adhesions.

Vaginal varicose veins are uncommon but may occur in older mares. They may be detected on speculum or vaginoscopic examination. Clinical signs may not occur, or there may be bleeding from the vagina. Most cases do not require treatment, but if the bleeding is severe, the veins may be ligated. The bleeding may recur, however.

Vaginal trauma may result from dystocia or breeding accidents in which the vaginal wall is torn by the stallion's penis. In either case, rapid detection is important. Suturing or surgical repair of the vaginal tear should not be done; systemic antibiotics should be administered to combat the possibility of peritonitis. Sexual rest is necessary until healing takes place. When breeding can be done again, a breeding roll, a device used to prevent the stallion from entering too far, should be used.

Rectovaginal fistula occurs when the foal's foot or feet tear through the vaginal roof and rectum. These need to be sutured, and it is often an unrewarding experience because fecal contamination of the area presents a challenge to healing.

Cervix

The cervix is an important barrier against ascending infection. When the mare is in season, it is pink, soft, and open, and the stallion's penis actually enters it so ejaculation occurs directly into the uterus. When the mare becomes pregnant or is in diestrus, the cervix is small, pale, and tightly closed. Shortly before foaling, the cervix softens and relaxes.

Cervical lacerations frequently occur during dystocia. They can be diagnosed by visual or manual examination, but the latter is necessary to determine the extent and severity of the laceration. Those that involve the full thickness of the cervix and the internal os (opening) are more serious and have a worse prognosis than those that involve only a partial thickness and the external os.

To determine the ability of the cervix to fully close requires the mare to be under the influence of progesterone, so it may be necessary to administer exogenous progesterone to see if it closes fully.

If the laceration is detected early (shortly after foaling), antibacterial ointment should be applied to it and any adhesions should be broken when the ointment is applied. If the laceration results in a cervix that does not close properly, surgery is necessary. This should be done during diestrus and the mare should not be bred for six to eight weeks following the surgery.

Although most cervical lacerations occur during dystocias, some occur as the result of breeding. In maiden mares, the cervix does not open as it does in mares that have had foals; a stallion with a large penis can tear it or the vaginal wall.

Cervical adhesions may result from lacerations of the cervix, cervicitis, or irritating substances used to treat endometritis. Adhesions may prevent the cervix from opening or closing fully, or they may occlude the cervix. A common result from a cervical laceration during a dystocia is an adhesion from the external os to the vaginal wall.

Cervical adhesions can be diagnosed by speculum or manual examination. Most adhesions can be broken manually or severed with long-handled scissors, but the breaking must be done daily for several days because they reform. An antibacterial-steroid ointment should be applied daily. The prognosis depends on the severity and extent of the adhesions.

Cervicitis may result from endometritis, urovagina, vaginitis, or trauma. An inflamed cervix may not close properly, predisposing the mare to uterine infection and a failure to become pregnant. On speculum examination, an inflamed cervix is dark red and swollen. Treatment depends on the cause.