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Vasectomy in birds: a review.

Abstract: Vasectomy is done to produce infertility by surgically removing a portion of the ductus deferens from both testicles. In birds, vasectomy can be done internally or externally. Internal vasectomy is performed by severing and removing a section of the ductus deferens through bilateral celiotomy or by endoscopic-guided techniques. Vasectomy can be done externally using standard surgical procedures in those species possessing seminal glomera. In this review, the surgical techniques used to perform vasectomy in birds and the implications and applications of each technique are discussed.

Key words: seminal glomus, testis, vas deferens, vasectomy, adrenal gland, epididimys, avian

Introduction

Vasectomy is the surgical removal of a portion of the ductus deferens on either side with the objective of inducing infertility. In birds, different surgical techniques have been used to perform vasectomy for different purposes, such as a method to control unwanted populations of redwinged blackbirds (Agelaius phoeniceus) (1) and Canadian geese (Branta canadensis) (2,3); to produce surrogate parents from wild-caught northern Texas bobwhite quail (Colinus virginianus texanus) for rearing the more endangered northern masked bobwhite quail (Colinus virginianus ridgwayi) chicks (4); to prepare teaser budgerigar (Melopsittacus undulatus) males for an artificial insemination program (5); for examination of the fertile period of the zebra finch (Taeniopygia guttata) and the Bengalese finch (Lonchura striata) (6); to sterilize immature birds by using the Japanese quail (Coturnix coturnix japonica) as a model (7); and to sterilize hybrid falcons destined for the sport of falconry. (8) In these species, vasectomy has been performed internally by severing and removing sections of the vas deferens through bilateral celiotomy (2-4,8) or by endoscopic-guided techniques. (7) Conversely, vasectomy has been done externally by using standard surgical procedures in those species possessing seminal glomera. (1,5,6)

The purpose of this article is to review the surgical techniques used to perform vasectomy in birds and to discuss the implications and applications of each of the techniques.

Anatomic Review

The ductus deferens is a tortuous tubule, which originates in the epididymis on the dorsal aspect of the testis, runs alongside the ureter, across the dorsal aspect of the coelom, and penetrates the dorsal wall of the urodeum, where it forms the short papilla of the ductus deferens. In seasonal species, its diameter increases significantly during the culmination phase of the breeding cycle. (9)

In many species of passerine birds (9) and in the budgerigar, (10) the caudal portion of the ductus deferens forms a paired, convoluted structure that denominates the seminal glomera, (9) located on the lateral lower section of the abdomen. During the culmination phase of the breeding cycle, the seminal glomera increase in size and volume, forming small, rounded swellings that bulge on either side of the cloaca. These swellings are commonly called the cloacal promontory. These structures can be used to determine the sex of passerine birds during the breeding season. In those species, the seminal glomera are used as a storage site maintaining the spermatozoa at 4[degrees]C (39.2[degrees]F) lower than the deep rectal temperature. (9)

Surgical Techniques

General considerations

Although some of the preliminary studies of vasectomy in birds were carried out either without anesthesia (2) or with injectable anesthetic agents, (5,6) inhalation anesthesia using isoflurane is now the most accepted and recommended method for achieving surgical anesthesia in birds. (11) Induction and maintenance of anesthesia is achieved with a custom-made facemask adequate for the size of the species. In a study of budgerigars and zebra and Bengalese finches (5) (J. S., unpublished data, October 2009), a small operating table made of an acrylic top and aluminum sides, measuring 20 cm long x 12 cm wide x 10 cm high, was used. The top was molded to accommodate the shape of small birds. A heating pad was placed underneath the operating table providing the operating table surface with a temperature (by conduction) of approximately 28[degrees]C (82.4[degrees]F). The use of this operating table greatly enhanced the ability of the attending veterinary surgeon to conduct the surgical procedure. (5)

Internal vasectomy

Internal vasectomy can be performed using standard bilateral celiotomy. After the bird is anesthetized, it is placed in right lateral recumbency, with the left leg pulled in the dorsal caudal position and the wings deflected dorsally. Legs and wings are securely fastened to the operating table with masking tape. The skin is incised from approximately the sixth rib to the pubic bone. The exposed superficial medial femoral artery and vein are cauterized with bipolar electrocautery forceps. A small incision is made on the external and internal oblique and transverse abdominal muscles, and the incision is enlarged by blunt dissection with fine, straight artery forceps. The intercostal blood vessels of the last 2 ribs (ribs 7 and 8) are cauterized with bipolar electrocautery forceps before severing the ribs with scissors. A small retractor is placed to allow adequate visualization of the coelom. The wall of the abdominal air sac is penetrated to expose the testis and the ductus deferens located on the ventral aspect of the anterior pole of the kidney. The ductus deferens is identified and carefully debrided with a blunt probe where it emerges from the epididymis. The ductus deferens is then grasped and severed by pulling gently with dissecting forceps or, ideally, biopsy forceps, and then a sizeable segment (5-8 mm) is removed by applying gentle traction to the opposite end. Ligature or hemoclip placement on the terminal ends of the ductus deferens is considered unnecessary. Extreme care should be exercised during the procedure to avoid any damage to the underlying common iliac vein or the ureter. The same procedure is done on the contralateral side. After completing the surgical procedure, the incision is sutured in a continuous or interrupted pattern in 2 layers using 4-0 or 5-0 absorbable suture. Comprehensive descriptions of the surgical procedure for lateral celiotomy in avian species have been described recently. (12,13)

Conversely, internal vasectomy can be performed in birds with a less-invasive surgical procedure based on an endoscopic-assisted technique. (7) The bird is placed in lateral recumbency with the legs pulled either in the caudal position (14) or with the upper leg pulled forward (15) and secured to the table with masking tape. Deflecting the wings dorsally and securing them to the table with masking tape is of utmost importance in preventing cylindrical rotation of the body during the surgical procedure. This is easily overlooked, in particular when using cloth type operating drapes over the body. The recommended surgical point of entry is either the lower end of the inverted triangle created by the last rib, the cranial edge of the pubic bone, and the flexor cruris medialis and flexor cruris lateralis muscles or at the midsection of the intercostal space between the last 2 ribs. (15) Commonly, a small skin incision is made (5 mm), followed by blunt penetration through the muscles with a pair of artery forceps. Immediately after, a 2.7-mm endoscope is introduced through an operating sheath (Karl Storz GmbH & Co KG, Tuttlingen, Germany). The wall of the abdominal air sac is penetrated by applying gentle pressure with the tip of the telescope. The ductus deferens is identified (Fig la) and carefully debrided as it emerges from the epididymis. The ductus deferens is then grasped (Fig 1b) and severed by pulling gently with biopsy forceps and a sizeable segment (5-8 mm) is removed by applying gentle traction to the opposite end (Fig 1c). The preferred site for internal vasectomy is where the ductus deferens emerges from the epididymis; at that spot, the ductus deferens is not yet closely associated with the ureter. (5,7,16) The same procedure is done on the contralateral side. Ligatures or hemoclips on the terminal ends of the severed ductus deferens are not necessary. Extreme care should be exercised during the procedure to avoid any damage to the underlying common iliac vein or the ureter. The skin is closed with 1 or 2 interrupted sutures of 4-0 or 5-0 absorbable suture material. Endoscopic-assisted vasectomy has been successfully done in immature Japanese quail (7) and, more recently, in immature and mature domestic pigeons (Columba livia). (16)

[FIGURE 1 OMITTED]

External vasectomy

External vasectomy is indicated in those species that possess seminal glomera. After inducing anesthesia, the bird is placed in dorsal position, and the legs are secured caudally with masking tape. The lower abdominal wall is plucked and prepared for surgery. A small surgical incision (3-5 mm) is made midway on the straight line between the cloaca and the pubic bone (Fig 2a). The use of some form of magnification is highly recommended. In studies with budgerigars (5) and zebra and Bengalese finches, (6) all external vasectomies were performed with a 10x operating microscope. In a more recent study in common house sparrows (Passer domesticus), (16) vasectomies were done successfully with the aid of a 6x surgical binocular loupe (Heine Optotechnik, Herrsching, Germany). The use of a fine blunt probe aids in debriding and differentiating the ductus deferens within the subcutaneous space (Fig 2b). After it is identified, the ductus deferens is grasped with fine-tip dissecting forceps and a small section (5-8 mm) is severed using fine-tip microsurgery scissors (Fig 2c). The same procedure is done on the contralateral side while maintaining the bird in the same position. Ligatures or hemoclips on the terminal ends of the severed ductus deferens are not necessary. The skin is closed by placing 1 or 2 interrupted sutures of 5-0 absorbable suture material. Correct placement of the stitches is essential to avoid exerting tension on the cloaca because tenesmus has been previously reported (5) in budgerigars during the postoperative period.

Postoperative fertility assessment

After vasectomy, assessing the effectiveness of the procedure using a functional assay is essential. Different techniques have been used in previous studies. In one study, (5) semen collection was attempted in vasectomized, male budgerigars at monthly intervals, followed by examination with standard light microscopy techniques of any fluid obtained during the process. Conversely, vasectomized red-winged blackbird males, (1) zebra and Bengalese finch males, (6) Eastern bobwhite quail (Colinus virginianus) males, (2) and Japanese quail males (7) were paired up with females and allowed copulation and egg laying. After oviposition and natural (1,2,6) or artificial incubation, (7) fertility was assessed through candling of the eggs (1,6) or by opening up and examining the internal contents of the eggs to assess fertility. (2,7) Vasectomy did not affect postsurgical breeding behavior, circulating plasma testosterone levels, or testicular morphometrics in immature Japanese quail, (7) findings that are similar to those found in other studies done on mammalian species. (17)

[FIGURE 2 OMITTED]

External vasectomy in passerine birds and internal vasectomy in nonpasserine birds can be done by following the surgical procedures described above. However, vasectomy does not arrest courtship and copulation, and radical orchiectomy should be considered as an alternative method to eliminate sexually derived behavior and to produce permanent infertility in birds.

Acknowledgments: I thank HH Sheikh Sultan bin Zayed Al Nahyan for his continuing support to the biomedical research program of the Veterinary Science Department, the veterinary technical and keeping staff for assistance with the surgery and the keeping of the birds, and Dr Jesus Naldo for kindly reviewing the manuscript.

References

(1.) Bray OE, Kennelly JJ, Guarino JL. Fertility of eggs produced on territories of vasectomized red-winged blackbirds. Wilson Bull. 1975;87:187-195.

(2.) Ellis DH, Carpenter JW. A technique for vasectomizing birds. J Field Ornithol. 1981;52:69-71.

(3.) Converse KA, Kennelly JJ. Evaluation of Canada goose sterilization for population control. Wildl Soc Bull. 1994;22:265-269.

(4.) Hundgen K, Raphael B, Sheppard C. Egg fertility among vasectomized and non-vasectomized male resident Canada geese at the Wildlife Conservation Park/Bronx Zoo. Zoo Biol. 2000;19:35-40.

(5.) Samour JH, Markham JA. Vasectomy in budgerigars (Melopsittacus undulatus). Vet Rec. 1987; 120: 115.

(6.) Birkhead TR, Pellatt JE. Vasectomy in small passerine birds. Vet Rec. 1989;125:646.

(7.) Jones RG, Redig PT. Endoscopy guided vasectomy in the immature Japanese quail (Coturnix coturnix japonica). Proc Eur Assoc Avian Vet. 2003:117-123.

(8.) Heidenreich M. Birds of Prey: Medicine and Management. Oxford, UK: Blackwell Science; 1995.

(9.) King AS, McLelland J. Birds: Their Structure and Function. London, UK: Bailliere Tindall; 1984.

(10.) Samour JH, Spratt DMJ, Holt WV, Smith CA. Ultrastructure and secretory nature of the seminal glomus in budgerigars (Melopsittacus undulatus). Res Vet Sci. 1988;45:194-197.

(11.) Lawton MPC. General anesthesia. In: Samour J, ed. Avian Medicine. 2nd ed. London, UK: Mosby Elsevier; 2008:137-151.

(12.) Forbes N. Avian soft tissue surgery. Proc Eur Assoc Avian Vet. 2009:419-431.

(13.) Bowles HL, Odberg E, Harrison GJ, Kottwitz JJ. Surgical resolution of soft tissue disorders. In: Harrison GJ, Lightfoot TL, eds. Clinical Avian Medicine. Vol 2. Palm Beach, FL: Spix Publishing Inc; 2006:775-829.

(14.) Lierz M. Diagnostic value of endoscopy and biopsy. In: Harrison G J, Lightfoot TL, eds. Clinical Avian Medicine. Vol 2. Palm Beach, FL: Spix Publishing Inc; 2006:631-652.

(15.) Samour J. Endoscopy. In: Samour J, ed. Avian Medicine. 2nd ed. London, UK: Mosby Elsevier; 2008:122-135.

(16.) Samour J. Vasectomy in birds. Proc Eur Assoc Avian Vet. 2009:15.

(17.) Whyte J, Sarrat R, Cisneros AI, et al. The vasectomized testis. Int Surg. 2000;85:167-174.

Jaime Samour, MVZ (Hons), PhD, Dipl ECAMS

From the Wildlife Division, Wrsan Farm, PO Box 77338, Abu Dhabi, United Arab Emirates.
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Author:Samour, Jaime
Publication:Journal of Avian Medicine and Surgery
Geographic Code:1USA
Date:Sep 1, 2010
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