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Neutering companion exotic mammals (Proceedings)

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Nov 01, 2009

One of the main reasons for neutering exotic pet mammals is to control reproduction. Medical and behavioral indications are also important factors to consider in making a decision to have a pet neutered. In most species, castration makes male mammals less aggressive both to other animals and to their owners. The urine of many intact male mammals has a more potent odor and is used for territorial marking. The odor and behavior can often be modified by neutering. In many species, mammary neoplasia is influenced by the presence of hormones and ovariectomy can decrease the occurrence of mammary cancer. Ovarian and uterine diseases are effectively prevented by either ovariectomy or ovariohysterectomy.

Basic principle

When neutering a mammal the goal is to remove the gonads which are responsible for hormone production. It is not necessary to pull the testicle out, far from the body risking accidentally tearing the vessels. The surgeon only needs the entire testicle exposed so the vessels can be ligated. Once transected (or torn) the vascular pedicle retracts into the retroperitoneal space as the testicular vessels are branches off the renal vessels. Hemorrhage from these vessels, therefore, occurs in the retroperitoneal space and does not cause hemoabdomen.

In species with a distinct scrotum, the scrotal skin is usually thinner and more delicate than the inguinal or the prescrotal skin. Therefore, I prefer to make the incision in the thicker inguinal or prescrotal skin if possible. It seems to bother the patient less and I believe they are less likely to bother their incision.

Closed castration describes removing the testicles along with the tunics without making an incision into the tunics. Open castration describes making an incision into the tunic (open) and removing the testicle, vas deferens, and associated vessels but leaving the incised tunic. In general, the testicles are easier to exteriorize using an open technique as the only attachment to other tissues is at the epididymis. With a closed castration, the external surface of the tunic is attached to the surrounding tissues. All of these attachments must be broken down to exteriorize the testicle. The main advantage to a closed technique is that it ligates the tunic near the inguinal canal minimizing the potential for an inguinal hernia to develop.

In the USA, ovariohysterectomy is generally recommended over ovariectomy alone. Investigations comparing ovariectomy to ovariohysterectomy support that removal of the ovaries but not the uterus is associated with no risk of uterine disease. Ovariectomy should be considered an effective alternative to ovariohysterectomy. It is not necessary to risk tearing the ovarian vessels in an effort to exteriorize the ovary far from the abdominal cavity. You only need to expose the vessels enough to effectively ligate them.

Ferret ovariohysterectomy

Ovulation is induced at breeding in ferrets. Unbred females remain in estrus until they are stimulated to ovulate by breeding or artificial means. A female ferret may remain in estrus for 6 months or more during which time the body's estrogen levels remain high. This chronic hyperestrogenemia can result in bone marrow suppression and, potentially, fatal aplastic anemia. Ovariohysterectomy should be performed as soon as the patient is stable. Blood transfusions are indicated in ferrets with a PCV < 30%.

Prevention by spaying females at 4-6 months of age or within the first two weeks of the first estrus is the best action. In the USA most ferrets are spay at an early age (5-6 wk) prior to arrival at pet stores. A CBC and platelet count should be evaluated on all intact female ferrets prior to ovariohysterectomy. Performing ovariohysterectomy in ferrets is analogous to that in cats with the ventral midline incision centered midway between the umbilicus and pubis. The uterus is bicornuate and the suspensory ligaments are loose and easily stretched or broken.

Spayed female ferrets that show clinical signs of estrus are usually affected with adrenal neoplasia or, rarely, have residual ovarian tissue. Female ferrets that have been spayed but that have residual ovarian tissue will generally present with vulvar swelling and signs of estrus at an earlier age (< 2 yrs age) than ferrets with adrenal tumors (> 2 yrs age). In most ferrets with ovarian tissue, vulvar swelling subsides following the administration of 100 IU of human chorionic gonadotropin, while in ferrets with adrenal disease this hormone has no effect. Though ectopic ovarian tissue has been reported in ferrets, in most cases residual tissue is a result of incomplete ovariectomy.