CASTRATION OF PIGLETS

Castration of pigs is routinely performed in attempts to improve performance, feed conversion, carcass traits, and make management easier than for intact pigs. Boar meat becomes tainted with an unpleasant odor and taste at the onset of puberty. However, age recommendations for pig castration vary. The stress of pig castration was evaluated at 1, 2, 4, 8, 16, and 24 days of age (White, et al, 1995). This study indicated that pigs castrated after administration of lidocaine anesthetic subcutaneously and around the spermatic cords had a lower heart rate and less vocalization than pigs castrated without local anesthesia. This effect was greatest for pigs castrated after 8 days of age. Behavioral changes associated with castration were evaluated in pigs castrated at 1, 5, 10, 15, and 20 days of age. Castration caused reduced suckling, reduced standing, and increased lying time in comparison to intact male pigs at all ages. Pigs castrated at 14 days old were heavier at weaning and had a higher gain rate in comparison to pigs castrated at 1 day old. Administration of aspirin or butorphanol failed to improve castration-associated reduction in feeding time and weight gain. Administration of lidocaine anesthesia before castration prevented castration-induced nursing behavior suppression in 2-week-old pigs. This effect was not observed for pigs castrated at 7 weeks old. Pigs castrated at 2 weeks of age had less pronounced behavioral changes than pigs castrated at 7 weeks of age. Therefore we recommend piglets be castrated at 2 weeks of age to minimize castration stress and maximize performance until weaning.

Two-week-old pigs can be castrated by suspending them by the hind limbs while they are laid across a smooth rail. The surgical site is prepared for aseptic surgery. If used, lidocaine anesthetic is injected subcutaneously (0.5 ml per site) into tissue overlying each testis and spermatic cord (0.5 ml per site) in the inguinal canal. A 1-cm incision is made over each testis, and the testes are pulled from the scrotum. Hemorrhage is minimal at this age. Ligation of the spermatic cord is recommended for older pigs (see Castration of Older Pigs). Topic antiseptic ointment or spray may be applied at this time. Systemic antibiotics are usually not required, except for castration of older pigs. Castrated piglets are placed under a heat lamp in the farrowing crate for convalescence.

CASTRATION OF OLDER PIGS

Veterinarians may be asked to castrate older pigs intended for show or mature boars that will no longer be used for breeding. Castration of older pigs is best performed with the pig sedated or under general anesthesia. The boar is restrained in lateral recumbency, and the surgical site is aseptically prepared (Figure 23-1A). A 4- to 6-cm incision is made overlying the testis at the ventral aspect of the scrotum. The testis should be removed with the vaginal tunic intact (Figure 23-1B). Inguinal fat and soft tissue are stripped from the spermatic cord and evaluated for the presence of an inguinal hernia. The vaginal tunic and spermatic cord are twisted until the cord is tightly compressed to the level of the external inguinal ring (see Figure 23-6). Two circumferential ligatures (No. 1 synthetic absorbable suture material) are placed around the vaginal tunic and spermatic cord. An emasculator (see Figure 4.4-8A and B) is used to complete the castration (see Figure 23-1B). Closure of the surgical wound is rarely done and should only be performed if asepsis has been maintained. We prefer to administer antibiotics for 3 days, beginning the day of surgery, to reduce the incidence of postoperative infection. Also, the animal should be kept in a clean, dry stall during this period.

Figure 23-1 A, Boar under general anesthesia in lateral recumbency prior to castration. B, The testes are removed within the vaginal tunic.

(Courtesy of Dr. Christopher Beinlich; Cornell University.)

Figure 23-6 Surgical repair of an inguinal hernia showing the tunic and testis being twisted to force the intestines into the peritoneal cavity.

The most common complications after pig castration are hemorrhage, abscess, scirrhus cord, inguinal hernia, and seroma or hematoma formation. Fatal hemorrhagic shock has been reported after castration of 7 week old pigs by a lay person. The testes had been pulled through a 10-cm incision and cut using a knife. Fatal hemorrhage occurred into the pelvic canal and abdomen; therefore the cause of death was not recognized until necropsy. This report emphasizes the need for routine necropsy to determine the cause of all non-apparent deaths. Meat inspection of 131 pigs with postcastration abscesses revealed that Actinomyces pyogenes, β-hemolytic Streptococci, Streptococcus viridans, Staphylococcus aureus, and Pasteurella multocida were the most common bacteria isolated. Approximately 65% of the abscesses were monomicrobial, and 35% were polymicrobial infections. Of the 131 pigs inspected, 11% were judged to be unfit for human consumption. Bilateral hydronephrosis also has been reported as a complication of castration in a Hampshire pig castrated at 8 weeks old. A ventral midline incision was used to remove both testes and tincture of iodine applied after castration. Infection of the soft tissues occurred, and the ensuing infection resulted in progressive occlusion of urethra at the level of the sigmoid flexure. Chronic resistance to urine outflow caused hydronephrosis, and the pig died 4 weeks after castration. This case illustrates the importance of adequate ventral drainage after castration.

UNILATERAL CASTRATION

Indications for removing only one testis include testicular trauma, torsion (Figure 23-2), hematoma (Figure 23-3), seroma, and orchitis or periorchitis. The damaged testis may cause enough swelling, heat, and pressure to reduce fertility. The boar is placed under general anesthesia, a 6-cm incision is made over the testis starting at the most ventral aspect of the scrotum, and the testis is removed by circumferential ligation and excision. The wound should be left open for drainage and second intention healing. Antibiotics are administered for 5 to 7 days, and daily hydrotherapy is used to minimize postoperative swelling. Affected boars may return to productive service 30 to 60 days after surgery.

Figure 23-2 Boar with testicular torsion. Note swollen hemorrhagic testis.

(Courtesy of Dr. Andre Desrochers; University of Montreal.)

Figure 23-3 Boar with testicular hematoma. Note swollen scrotum.

(Courtesy of Dr. Andre Desrochers; University of Montreal.)

INGUINAL HERNIA

Inguinal hernia results when a defect permits intestines or other abdominal organs to pass into the inguinal canal. The hernia develops when an abnormally large and patent vaginal ring allows free communication between the vaginal tunic and peritoneal cavities. Organs protrude into the scrotum to form a scrotal hernia, a more exaggerated form of the defect (Figure 23-4). These hernias are common in swine. The frequency of inguinal hernia among the porcine population varied between 0% and 15.7%, with a realistic estimate of approximately 1%. The development of these hernias seems to be genetically influenced. One study indicated that the variation associated with anatomic structures relevant to scrotal hernia is influenced polygenically. In that study, the heritabilities of susceptibility to scrotal hernia development were estimated to be 0.29, 0.34, and 0.34 in Duroc, Landrance, and Yorkshire-sired pig groups, respectively. Inguinal (see Figure 23-4) and scrotal hernias need to be differentiated from hydrocele, scirrhous cord, and hematoma (see Figure 23-3) of the testis. Diagnosis is made by historical data (e.g., a pig that has been castrated before is more likely to have a scirrhous cord) and direct manipulation. If necessary, ultrasonography and needle aspiration can be used. Inguinal hernias often are encountered at the time of castration. Some of these hernias will reduce spontaneously but recur later. With chronic inguinal hernia, intestinal incarceration and strangulation may be observed.

Figure 23-4 Pig with a scrotal hernia restrained in dorsal recumbency. Note swelling in left scrotum and left inguinal area (arrow).

Surgical repair of an inguinal or scrotal hernia is easier before the pig is castrated. With the pig restrained in dorsal recumbency and its rear quarters elevated, the inguinal and scrotal area is thoroughly cleaned and prepared for surgery. An oblique incision is made over the affected superficial inguinal ring (Figure 23-5). Once the incision pierces the skin, the subcutaneous tissue is dissected bluntly. The tunica vaginalis is also isolated by blunt dissection (see Figure 23-5). The tunica vaginalis should be kept intact, because this will keep the intestine contained. While external pressure is put on the scrotum, the tunics are gently pulled free from their scrotal attachment. The tunic and testis are then twisted to force the intestines into the peritoneal cavity (Figure 23-6). The tunics and spermatic cord are transfixated as close to the superficial inguinal ring as possible. The tunic and cord are cut, and the superficial inguinal ring is closed with interrupted or horizontal mattress sutures. The herniorrhaphy site is checked by applying external pressure on the abdomen. The skin is closed using absorbable sutures. The authors recommend checking the opposite inguinal ring for possible bilateral herniation before performing a castration. If the surgery was done to repair a large hernia in which marked serum accumulation in the scrotum is expected, an incision in the most ventral aspect of the scrotum should be performed to provide ventral drainage. If intestinal adhesion and incarceration are observed during surgical correction, the vaginal tunic should be opened and the intestine dissected free or an intestinal resection and end-to-end anastomosis performed. If an inguinal hernia occurs after castration, one needs to clean and lavage the herniated bowel, enlarge the vaginal and superficial inguinal ring, and replace the prolapsed intestine (if it is judged still viable) before suturing the superficial inguinal ring closed.

Figure 23-5 Pig restrained in dorsal recumbency; an oblique incision is made over the affected superficial inguinal ring and the vaginal tunic isolated.

(Courtesy of Dr. Andre Desrochers; University of Montreal.)

CRYPTORCHIDISM

Veterinarians may be presented with barrows (male hogs castrated before sexual maturity) that demonstrate boar-like traits for removal of retained testicular tissues. The testes of swine descend in the last 30 days of gestation and should be palpable at birth. True cryptorchidism (testis not descended at birth) is a common congenital defect in swine. A homozygous recessive trait involving two gene loci has been postulated based on a breeding trial of cryptorchid Duroc swine. Cryptorchid testes are usually intraabdominal and are found midway between the ipsilateral kidney and deep inguinal ring. However, the affected testis may be located within the inguinal canal and not readily palpable from either the inguinal region or peritoneal cavity. Previous removal of the descended testis makes surgical removal of the retained testis more difficult because the incision is best made over the affected superficial inguinal ring. Often, determining which testis has been removed is difficult. The authors prefer to perform cryptorchid surgery with the pig under general anesthesia. A 6-cm incision is made over the appropriate superficial inguinal ring. Laparotomy may be performed by making an incision 1- to 2-cm medial to the inguinal canal (parainguinal incision), or the superficial inguinal ring may be enlarged by starting the incision at the cranial commissure of the superficial inguinal ring. The fingers of one hand are used to perform an exploration of the abdominal cavity, starting at the pelvic brim and searching along the dorsal and lateral abdominal wall until the kidneys are encountered. For show pigs, we prefer to perform laparoscopic exploration and removal of abdominal testes because better cosmesis, fewer incisional complications, and more rapid incisional healing are achieved.

True cryptorchidism should be differentiated from ectopic testicular tissue. Ectopic testicular tissue has been observed in numerous pigs at the time of slaughter. These tissues occur as smooth, pink, or tan nodules on the surface of the liver, spleen, mesentery, and other abdominal viscera. Initially, these masses may be interpreted as metastatic neoplasia, but histology reveals the presence of convoluted seminiferous tubules and interstitial cells. No evidence for neoplasia is seen. Ectopic testicular tissues may be found in castrated or intact male pigs.

PREPARATION OF TEASER BOARS

Vasectomy or epididymectomy is done to produce teaser boars—which are used to detect sows in heat for artificial insemination or breeding to valuable boars—or to promote onset of cyclicity in confined gilts (young females). For vasectomy, the boar is placed in dorsal recumbency under general anesthesia, and a 4-cm incision is made over each spermatic cord approximately 6 cm cranial to the ventral aspect of the scrotum. Each spermatic cord is elevated and incised, and the ductus deferens isolated. The ductus deferens is firm and pale, and an arterial pulse is not present (see Figure 19.1-10). A 3- to 4-cm segment of the ductus deferens is excised and each end ligated. The incision through the tunic is sutured with No. 2-0 PDS synthetic absorbable suture material, and the skin is sutured with No. 0 nonabsorbable suture material in a simple interrupted pattern. Epididymectomy is done by making a 2-cm incision in the scrotum overlying the tail of the epididymis. The tail and 1 cm of the body of the epididymis is isolated. Ligatures are placed between the testis and the tail of the epididymis and around the exposed portion of the body of the epididymis. The epididymis is excised between these two ligatures. The skin is closed with No. 0 nonabsorbable sutures in an interrupted pattern.