Castration

Castration is the most common surgical procedure performed on bulls. Despite the relative simplicity of the procedure, many factors contribute to success or failure, including bull size, facilities, location, weather conditions, pre- and postsurgical environment, surgical method including speed and cleanliness, and other pre- and postsurgical stresses. The most common postsurgical complications include severe hemorrhage, wound infection with cellulitis and potentially fatal septicemia, inadvertent damage to the penis, and, rarely, intestinal herniation through the inguinal ring.

Two factors are important to consider in castrating bulls: (1) timing of the procedure and (2) selection of the method to be used. Bulls should be castrated early in life (at 1 to 3 months of age) because performing the procedure then is less stressful and more humane and better addresses animal welfare concerns. When given a growth-promoting implant, steers will reach market size about the same time as do intact bulls.⁴ On ranches with a defined calving season, early castration is more easily coordinated. On those farms where calving occurs year round, however, castration at the ideal time necessitates performing castration in groups of animals several times a year. This approach is rarely used, and bulls tend to be castrated at weaning or sold as bulls and castrated at the feedlot or stocker operation. In the purebred industry, castration is purposely delayed to allow consideration of the better bulls for sale as breeding animals. Bulls can be castrated by open or closed techniques. Closed methods involve the use of rubber bands or the Burdizzo method (emasculatome). Open methods require surgical opening of the scrotum to remove the testicles. An economic evaluation of methods of castration has been reported.⁴

The objective of surgical castration is to remove both testes quickly in the cleanest environment possible. Depending on their size, bulls can be castrated while standing or recumbent and held by an assistant(s) or confined to a squeeze chute. Because of time constraints, the procedure usually is performed without anesthesia. Nevertheless, injection of 2% lidocaine directly into each testis will provide some analgesia. In the not-too-distant future, veterinary practitioners may well be compelled to provide analgesia for some procedures in cattle routinely performed without anesthesia for literally thousands of years.

To free the testes from the scrotum, a castrating knife^* (Newberry knife) can be used. The knife is applied transversely across the base of the scrotum, closed, and pulled ventrally to open both scrotal sacs without removing any scrotal tissue, thereby preserving the scrotum (cod). An alternative method is to grasp the apex of the scrotum with one hand, stretch it ventrally, and with a scalpel in the other hand, excise the distal one third of the scrotal sac in one swift cutting motion. In both techniques, the tunica vaginalis should not be incised, and the testes are removed in a closed fashion. Once the testes are freed, the “one clean hand, one dirty hand” technique is used to free the spermatic cords from the surrounding fascia. The “dirty” hand grasps the testis (both testes, if small enough) and maintains ventral traction while the “clean” hand strips the fascia free by pushing the skin proximally. The testes are then removed by application of an emasculator proximal to each testis. Tension on the testis should be minimal at the time of emasculation. After the testes are removed, excess scrotal adipose tissue is trimmed from the wound and clostridial vaccines are administered if the patient was not immunized before the procedure.

An alternative to emasculation is ligation of each spermatic cord. Closed castration with a rubber band has been popular in smaller bulls for a number of years. A latex band (commonly used in sheep) can be applied proximal to both testes around the neck of the scrotum. It is important not to place the band so high on the scrotum as to risk injuring the penis. In recent years, castration of large bulls with rubber bands has become more popular with the development of newer equipment designed for the purpose. This method is particularly popular in feedlots. This closed technique uses an instrument^* that allows rubber tubing to be stretched and clamped very tightly around the scrotal neck. Avascular necrosis of the scrotum and testes results. Done properly, this is a very effective castration method, and the animals are reported to undergo minimal stress.

All castrated animals should be immunized against clostridial organisms, particularly those causing blackleg and malignant edema. In addition, if rubber bands are used, protection against tetanus must be considered, particularly in large bulls in feedlot situations. Tetanus antitoxin can be used but is relatively expensive; vaccination with products containing tetanus toxoid at the time of castration have proven effective. After castration, animals should be placed in a clean environment, given the opportunity to exercise, and observed periodically over the subsequent 24 hours.

Epididectomy

Epididectomy is discussed later under “Preparation of Teaser Animals” later in the chapter.

Tumor Removal

The most common neoplasm found on the penis of bulls is a viral fibropapilloma. Such growths are common in young bulls housed together and undoubtedly are associated with the homosexual activity this management practice encourages. The lesion is caused by the bovine papillomavirus, which enters the skin through abrasions.

Affected young bulls frequently are presented with the complaint of hemorrhage from the preputial orifice, usually after coitus. Fibropapillomas also may be incidental findings when a breeding soundness examination is performed. On rare occasions, the bull may be presented with the complaint of phimosis and swelling in the sheath. This can result when the papilloma is of sufficient size to cause pressure necrosis and swelling within the preputial cavity, which prevents penile extension.

Papillomas can be single or multiple and frequently are located on the free end of the penis and less commonly on the preputial skin. They tend not to be invasive, and although the tumor may appear large, the area of attachment often is relatively small. Blood supply to the fibropapilloma is significant, and removal of the tumor may require ligation or cautery.

The procedure can be performed with or without mild tranquilization, depending on lesion size, location, and the bull’s demeanor. A pudendal nerve block may also be considered. Tail-stand restraint is sufficient to complete the surgery in most cases, however. To maintain extension of the penis, a cotton gauze bandage is used to get a firm grasp on the glans penis, and another is tied around the penis proximal to the tumor to act as a tourniquet and to assist in keeping the penis extended.

The penis is prepared for surgery with a surgical scrub. Local anesthetic is infiltrated to block the dorsal penile nerves by injection beneath the preputial skin on the dorsal surface of the penis at the level of the external preputial orifice.

The objective in removing a fibropapilloma is to excise it at the base of the lesion. To obtain adequate access to the base of an extensive tumor, a large portion of the mass can be simply cut away. At the base, an elliptical incision is made in the epithelium, leaving a stalk attached to the fibropapilloma. The stalk is ligated with size 0 polyglycolic acid^* to prevent postsurgical hemorrhage. The stalk is severed, and the epithelium is closed over the wound. If the tumor is close to the urethra, it is advisable to insert a catheter as a guide to avoid accidental incision of the urethra.

In my experience, laser technology has proved to be a very effective method of removing penile warts, and as the costs of laser equipment decline in the future, it is hoped that this technology will become an economically viable alternative to standard surgical management.

Postoperative complications are rare after fibropapilloma removal. The bull should be withheld from breeding for 2 to 3 weeks, however, and examined before return to service. Regrowth of fibropapillomas occurs occasionally, and vaccination with a commercial or an autogenous wart vaccine may reduce the recurrence rate. Under certain management systems or in particular environments, penile fibropapillomas can affect a significant number of bulls. In these instances, management practices should be changed to avoid co-mingling large numbers of young bulls. A wart vaccine may be administered in an effort to reduce the incidence, although in my experience, vaccines have not been very effective.

Correction of Persistent Penile Frenulum

A persistent penile frenulum is recognized during a breeding soundness examination or when a young bull is placed in service for breeding. The condition arises when the penis fails to separate completely from the prepuce by 12 months of age. The penis and prepuce are fused at birth in the bull and separate as a result of testosterone stimulation beginning at 4 to 6 months of age. Persistent penile frenulum is suspected to be a heritable condition, and clients should be informed before corrective surgery is performed.

In most cases, a fibrous band extends from the prepuce and attaches to the ventral median raphe immediately caudal to the glans penis. On rare occasions, more than a single attachment point may be present, or the attached area is several centimeters long. The surgical procedure entails extension of the penis, surgical preparation of the area, and ligation of the frenulum with absorbable suture material at the preputial and penile extremities. The tissue is then severed between the ligatures. In those cases in which more than a single point of attachment is present, the other points are ligated and severed in a similar manner. Usually, hemorrhage is minimal. An antibiotic ointment can be applied postoperatively and the bull withheld from breeding for approximately 2 weeks. In cases characterized by a broad area of attachment between the penis and prepuce, corrective surgery must be discouraged.

Rupture Repair in Penile Hematoma

The classic penile hematoma is the result of rupture of the tunica albuginea and subsequent escape of blood from the corpus cavernosum penis (CCP) into and around the elastic layers surrounding the penis. During erection, very high blood pressures in the CCP have been measured.⁵ Severe downward deviation of the erect penis during mating may cause a transverse tear through the tunica albuginea into the CCP and permit the release of blood. The injury in the tunica albuginea frequently is on the dorsal surface of the penis opposite the attachment of the retractor penis muscles; however, other rupture sites have been reported.^6,7

The objective of the surgical procedure is to close the rent in the tunica albuginea, rather than allowing the injury to heal spontaneously. The view of some clinicians is that surgical closure of the rent results in a stronger union and a reduced likelihood of recurrence or shunt formation. This is a controversial point, however, and the decision to perform surgery should be based on elapsed time since the injury occurred, the economic value of the bull, and whether or not the owner places sufficient value on the bull to consider collecting and storing frozen semen after surgery. If semen preservation is not a course the owner wishes to consider, then surgery is not indicated. This recommendation is based on the fact that greater than 50% of bulls with this injury that are treated medically (with 10 to 14 days of systemic antibiotic therapy) successfully return to service.

The typical presenting signs include a swelling of variable size located immediately cranial to the scrotum. The location alone often constitutes sufficient evidence to differentiate a penile hematoma from a peripreputial abscess. Preputial prolapse and swelling of the sheath frequently accompany penile hematomas and are the result of compromised venous drainage and development of dependent edema. The prolapsed prepuce may be traumatized, necessitating appropriate treatment. It is extremely rare for a peripreputial abscess to be located immediately cranial to the scrotum. These lesions typically are located in the mid-sheath area. In addition, the clotted blood in and around the elastic layers that surround the penis and adjacent tissue makes identification of the penis within the swelling difficult. If doubt still exists as to the contents of the swelling, aspiration (using a 16-gauge, 4-inch needle) after aseptic skin preparation and ultrasonography are alternative diagnostic procedures. If surgery is elected, it should be performed within 7 days of the injury, after which organization of the clot makes exteriorization of the penis, removal of the clot, and access to the tear in the tunica albuginea more difficult. Antibiotics should be administered as soon as the decision for surgery is made.

With the bull in right lateral recumbency and under general anesthesia or heavy tranquilization and local anesthesia of the incision site, the skin over the swelling cranial to the scrotum is shaved and prepared for surgery. The surgical area is draped, and an incision is made through the skin over the most prominent part of the swelling. This incision should be made in a cranioventral direction through the skin and subcutaneous tissue into the hematoma. Occasionally, the penis may be displaced and located just beneath the capsule of the hematoma, and care must be exercised in making the incision. This incision should be large enough to allow the surgeon’s fingers into the cavity to remove the clotted blood. If little organization of the hematoma has occurred, the penis can be grasped and easily exteriorized. The area of the attachment of the retractor penis muscles is identified. Careful dissection through the elastic layer of the penis dorsal to this area usually reveals the rent in the tunic. Dissection of the elastic layer must be in a longitudinal direction to avoid damage to dorsal penile blood vessels and nerves. In fresh cases, dissection is relatively simple. In instances in which significant organization of the clot has already occurred, careful dissection and retraction are required to free the penis and facilitate exteriorization. Further careful dissection through the elastic layer is necessary to clearly expose the rent.

The edges of the rent are débrided and sutured with size 1 polyglycolic acid in a simple interrupted or cruciate pattern. It is not necessary to suture the elastic layer around the penis. The hematoma cavity should be thoroughly flushed with an antibacterial solution (5,000,000 IU potassium penicillin in 1 L sterile saline) before closure. The subcutaneous tissue can be sutured with a continuous pattern using size 0 polyglycolic acid. The skin is sutured with 0.6-mm nylon^* in a continuous interlocking, cruciate, or horizontal mattress pattern. Postoperative care must include 10 days of systemic antibiotic therapy.

Complications are rare after aseptic surgery, but occasionally a seroma forms at the surgery site. This should not be drained, because abscess formation could follow. Within 7 to 10 days after surgery, the swelling will subside. The skin sutures can be removed at 12 to 14 days. The bull must have complete sexual rest for 60 days. After this period, the bull should be examined for the ability to successfully extend the penis and attain and maintain a normal erection. Sensitivity of the glans penis can be checked by application of a mild pain stimulus. If the bull’s reproductive function appears normal, semen can be collected and frozen, or he can be returned to service at 60 to 90 days after surgery.

Four sequelae are possible after this procedure. The first is abscess formation, which requires drainage and usually results in peripenile adhesions and permanent inability to extend the penis. The second is desensitization of the glans penis due to damage to the dorsal penile nerves at the time of injury, during surgery, or after healing and return to service, when adhesions involving the nerves may break down, allowing the nerves to be severed during erection. Third, peripenile adhesions can develop, resulting in fixation of the penis; in the absence of postsurgical infection, however, this is rare. The fourth possible sequela is development of vascular connections (shunts) between the internal blood supply of the CCP and the external vasculature of the penis and prepuce. With formation of such shunts, the CCP is no longer a closed system, and sufficient pressure for normal erection cannot be maintained. The shunts can be identified by contrast radiography, and an attempt can be made to surgically excise them. Vascular shunts are quite rare, and the method for surgical correction has been described.⁸