Male reproductive tract and orchidectomy

(castration surgery)

Esther van Praag, Ph.D.

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Warning: this file contains pictures that may be disturbing for some persons.

The reproductive organs of the male rabbit are very similar to that of other mammals, except for the additional ability to retract the testis in the abdomen. They are formed during the embryonic phase. They derive from primitive ancestors of the kidney tubules and the ducts, except for the lobules of the testes and the vasa recta. The blood vessels of the kidney will furthermore be used and deviated in order to supply the testes and the scrotal wall with blood.

MediRabbit Genital area showing the scrotum and testicle in a young male rabbit.	MediRabbit Penis of a young 4 month’s old male rabbit.
Michel Gruaz Rarely, the tip of the penis is haired.

The reproductive organ of the male rabbit is composed of different structures. One of them are the testes, which is composed of various components:

• Scrotal sacs: they are located in the inguinal area, ventrally to the anus and can be compared to a sac surrounded by skin and composed of muscles or connective tissue. They contain the testes.

• Testes: they are the reproductive gland, which is composed of tubular loops, lobules and a central tubular plexus (vasa recta).

The tubular lobules are lined with cells that develop the sperm, through a process of cell divisions (meiosis) and maturation. The sperm is brought to the tubular plexus (vasa recta). The later structure is furthermore lined with endocrine cells, secreting testosterone.

• epididymis: this is a coiled tube located at the surface of the testes

The testes descent into the scrotum at the age of 2,5-3 months, and castration surgery is usually done at the age of 4 or 5 months. Male rabbits possess a life-long ability to move freely their testis between the scrotum and the abdomen, via the inguinal ring. The response occurs during handling and examination, or during a fight between 2 males. Indeed, entire male rabbits will inevitably fight and attempt to “neuter” the other male by biting in the scrotal region.

Sebaceous (fat) glands surround the external genital parts of female and male rabbits. They are often not visible, except when full with a white fatty secretion. Here in a 5 year old castrated rabbit.

Why castrate a male rabbit and when ?

The castration of male rabbits is recommended in order to reduce difficult behavior, like the marking of its territory with strong smelling urine, aggressive attitude and mounting of objects or human body parts like feet and arms.

MediRabbit

Spraying by young male rabbit on furniture

Miela Mohd

Torn skin in the genital area after a fight between 2 non-castrated rabbits

Further medical reasons to favor the castration surgery include:

• chronic difficult to treat orchitis or epididymitis

• neoplasia of the testes, though this is rare in rabbits.

Castration of male rabbits is done only after the testes have descended into the scrotal sacs or little after. This happens around the age of 3 months. Young males can, thus be castrated anytime between 3 to 6 months of age. Dwarfs have usually a rapid development and can be castrated at the age of 3 months or little after. Some veterinarian want, indeed, to wait one or two weeks after the descent. Middle sized rabbits can be castrated after the descent of testis, between 3 and 4 months of age, depending on the breed. Bigger sized rabbits have a slower development and castration is usually done between 4 and 6 months of age.

If a male rabbit is not castrated shortly after the descent of the testis into the scrotal sac, sexual behavior, spraying the environment with urine and/or mounting feet and arms or aggression may become a settled behavior. The secretion of testosterone will also lead to the development of a typical strong body structure with a heavier head. Once neutered, these males may calm down. Some do, however, continue to spray and mount/aggress their rabbit companion.

Orchidectomy is done under general anesthesia. It is a surgical procedure that requires sterile surgical instruments and a preparation of the skin, in order to minimize infection.

Various surgical approaches are available for orchidectomy in rabbits, described in books, videos, or scientific articles. The following pictorial orchidectomy has been done according to the exterior extraction of the testis technique.

Pictorial castration surgical procedure

1 Once the rabbit is anesthetized, and positioned in dorsal recumbence on a heating pad, the fur around the scrotum sacs is shaved and the skin is scrubbed with a special surgical soap and an antiseptic solution. This step needs to be done carefully as rabbit skin is thin, friable and can easily be injured by tearing. The rabbit is monitored by pulse oximetry and a respiratory monitor.	2 A 1 cm incision is made through the skin, at the cranial end of the scrotum. The skin incised by means of scalpel or laser (longer procedure, but reduced bleeding).
3 The fibrous tunic is incised in order to isolate the testis and the connecting vessels. The vaginal tunic is exposed.	4 The tunic is localized and the testis is exteriorized.
5 The testis, epididymis and the deferent duct are pushed and advanced through the incision.	6 The deferent duct and the blood vessels are clamped and sutured. An additional suture is needed around the entire structure, in order to close the inguinal ring and prevent herniation of the abdominal content, unless a closed castration technique is used.
7 The isolated structures are carefully inspected, before removal of the testis by cutting through the well-sutured spermatic cord. The latter is important in order to avoid post-surgical scrotal hemorrhages. The final step is cutting of the ligament of the epididymis and the testis. No bleeding should happen at this stage of the surgery.	8 The remaining tissue is carefully replaced within the incision. Some surgeon’s recommend suturing or gluing the scrotum with acryl amide based products.
9 The incision is closed by placing sutures in the subcutaneous tissues and in the skin level. Since rabbit are notorious in breaking suture, it is recommended to do several subcutaneous layers.	10 Removed testes.
11 24 hours after castration surgery.

Post-surgical care

The administration of pain medication for at least 24 h. after the surgery is highly recommended. Pain indeed induces hormonal and physiological responses, which slow down the activity of the digestive tract, delay food intake and recovery.

The presence of blood in the urine during 24 to 48 h post-surgery is normal. Sometimes, the scrotum is filled with blood and hemorrhaged. In rare cases, blood is observed to leak through the sutures. Bleeders, small blood vessels that cannot be ligated, cause this bleeding. It is a non-dangerous nuisance that can last a few days. The administration of vitamin K can help accelerate clotting, if the bleeding is still present after a few days.

If the male rabbit was adult and fertile, he should be confined for 7 to 10 days, and kept separated from non-spayed females at least 4 weeks post-surgery. While sperma does not survive long in the male reproductive system after the castration surgery, the level of testosterone hormone take much longer to decrease in the blood. This is why male behavior may continue a few weeks after castration. The neutered rabbit is, however, no more able to fertilize a female rabbit.

Younger non mature males can be left with the female partner after a week already.

With time, a strong bond develops between rabbits that have been castrated.

Karan Nixon

Wendy "squashing" Binky Bear, or ultimate love between two bonded rabbits.

Acknowledgement

Many thanks to Michel Gruaz (Switzerland), Miela Mohd (USA), Karan Nixon (USA) and Akira Yamanouchi (Veterinary Exotic Information Network, Japan) and to Karan Nixon for the permission to use their pictures to illustrate this page.

Many thanks also to Wendy, BB and Zippy rabbits, for their collaboration.

Further Information

Gilsanz V, Roe TF, Gibbens DT, Schulz EE, Carlson ME, Gonzalez O, Boechat MI. Effect of sex steroids on peak bone density of growing rabbits. Am J Physiol. 1988; 255(4 Pt 1):E416-21.

Hussein SA, Azab ME, Abdel-Maksoud H. Metabolic changes concerning the effect of castration on some blood constituents in male rabbits. Dtsch Tierarztl Wochenschr. 1999; 106(3):113-8.

Jenkins JR. Surgical sterilization in small mammals. Spay and castration. Veterinary Clin North Am Exot Anim Pract. 2000; 3(3):617-27, v. Review.

Millis DL, Walshaw R. Elective castrationsd and ovariohysterectomies in pet rabbits. J. Am. Anim Hosp. Assoc. 1992: 491-497

Quesenberry KE, Carepenter JW, Quesenberry P. Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery Includes Sugar Gliders and Hedgehogs, Elsevier Health, 2004.

Smith K. Rabbit Health in the 21st Century. A Guide for Bunny Parents, Second Edition http://rabbithealth101.com/

Harcourt-Brown F. Textbook of Rabbit Medicine, UK: Butterworth-Heinemann, 2001, 192 page

Flecknell P , editor. BSAVA Manual of Rabbit Medicine and Surgery, Gloucester, UK: British Small Animal Veterinary Association, 2000.

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