Bovine Reproduction. Группа авторов
Читать онлайн книгу.
21.9 Securing the stay sutures for penopexy.
Source: Illustration by Mal Hoover.
Allow three to four weeks of recovery to ensure proper formation of adhesions. The drawback of penopexy is the risk of entering the urethra and decreased longevity in the herd since the bull will experience pain during attempted erection, thus decreasing libido. A follow‐up study of 37 bulls found that 15% of bulls maintained good libido for one breeding, 30% for 1–1.5 years, and 42% for more than 1.5 years [5, 8].
A standing perineal penopexy approach has been described using light sedation and a caudal epidural. The approach is over the distal loop of the sigmoid flexure [4]. A 4‐ to 5‐cm incision is made through the skin and the tunica albuginea is exposed as mentioned previously. However, the stay sutures are placed on the lateral aspects of the penis and secured to the fibrous connective tissue in the perineal region of the bull [4, 5].
Preputial Pouch Technique (Ventral Slot with Preputial Orifice Obliteration)
The preputial pouch technique creates a fistula on the ventral prepuce and closes the normal preputial orifice. This technique prevents penile extension but allows for passage of urine through the ventral fistula. Teaser bulls with a preputial pouch are typically retained in the herd longer because libido is maintained for longer due to the lack of pain during attempted breeding [5]. This procedure is performed in lateral recumbency and can be accomplished with tilt chute restraint or sedation with local infiltration of 2% lidocaine. The ventral abdomen is clipped and prepared from the umbilicus to the midsheath region of the bull.
Prior to initiating surgery, the penis is extended and a Penrose drain is sutured around the glans penis with 2–0 polydioxanone (PDS). An approximately 1‐cm‐diameter elliptical incision is made through the skin 7 cm caudal to the preputial orifice (Figure 21.10). The skin incision is extended through the preputial mucosa. The excised skin and mucosa are discarded. Then the internal mucosa of the prepuce is sutured to the skin of the sheath to create the fistula. An interrupted non‐absorbable suture pattern is recommended (Figure 21.11a and b) [5]. Once suturing is complete, the free end of the Penrose drain is placed through the fistula. The Penrose drain will facilitate urine divergence while the primary incision sites heal.
Figure 21.10 Site for incision for ventral fistula.
Source: Illustration by Mal Hoover.
Figure 21.11 (a and b) Suturing of preputial mucosa to the sheath skin.
Source: Illustration by Mal Hoover.
The preputial orifice obliteration is accomplished by removing approximately 5 mm of the sheath skin and prepuce mucosal junction around the entire preputial orifice (Figure 21.12). This incision is closed in three layers: preputial epithelium, subcutaneous layer, and skin. The Penrose drain and sutures can be removed in two weeks. Allow three weeks of postoperative recovery time prior to utilizing the teaser bull [5].
Figure 21.12 Excision of 5 mm of the preputial epithelium and sheath skin junction.
Source: Illustration by Mal Hoover.
The critical step in the preputial pouch technique is the size of the fistula. If the fistula is too small, proper urine flow is obstructed. If the fistula is too large, penile extension can occur with potential breeding. Therefore it is recommended to perform a vasectomy or epididymectomy to ensure sterility of the bull. Some bulls may pool urine in their preputial pouch and require postoperative flushing of the pouch. Thus this technique is not recommended for Bos indicus breeds since their pendulous sheath would predispose them to urine pooling and calculi formation [5].
Other Procedures
Other teaser bull procedures include iatrogenic preputial stenosis, artificial corpus cavernosal thrombosis, transection of the apical ligament, and penectomy. These procedures are briefly discussed, since their use has fallen out of favor due to high risk of failure, complication rates, and diminished libido.
Iatrogenic preputial stenosis involves a ventral midsheath approach to the prepuce and penis. The prepuce is identified and a stainless‐steel rod or Steinmann pin is secured and tightened around the prepuce. Care must be taken to tighten the ring sufficiently to prevent penile extension, but loose enough to prevent urine pooling and balanoposthitis [5, 9]. Mixed success rates accompany this procedure. Complications associated with this procedure include excessive ring closure resulting in urine retention and balanoposthitis, complete stenosis resulting in subcutaneous urine accumulation, lack of stenosis resulting in penile extension and intromission, and excessive tissue reaction to the stainless‐steel ring.
Corpus cavernosal thrombosis involves injection of an acrylic material into the corpus cavernosum of the penis [10]. The acrylic material results in thrombus formation that prevents erection. This method is performed with standing restraint under a caudal epidural. A midline incision is made over the penis. The distal sigmoid flexure is identified by locating the retractor penis muscle, with the proximal sigmoid flexure being approximately 15 cm proxi mally. A 14‐gauge needle is inserted at the dorsolateral aspect of the penis at the proximal sigmoid flexure and the acrylic is injected. Non‐absorbable stay sutures are placed at the lateral aspect of the penis at the level of the retractor penis muscle to prevent penile prolapse. Potential complications of this procedure include inadequate injection of acrylic into the corpus cavernosum resulting in procedure failure, or accidental injection into the corpus spongiosum or urethra resulting in urethral obstruction [5].
Transection of the apical ligament involves intentional transection of the apical ligament of the penis creating a ventral penile deviation and preventing intromission. The bull is restrained in lateral recumbency, either with heavy sedation and rope restraint or utilization of a tilt table. The penis is extended and a towel clamp is placed around the apical ligament of the penis to maintain penile extension. Prepare the penis and prepuce aseptically. Just proximal to the clamp, 2% lidocaine is infused subcutaneously under the epidermis of the penis. An approximately 2‐cm skin incision is made longitudinally along the dorsum of the penis. Once the apical ligament of the penis is isolated, the ligament is transected extending to the tunica albuginea. The skin incision is closed with interrupted absorbable suture. Possible complications of this procedure include excessive hemorrhage with secondary seroma or abscess formation. Additionally, inadequate transection of the apical ligament could occur or healing of the ligament could allow breeding occurrence, so a vasectomy or epididymectomy is recommended in conjunction with this procedure.
Penectomy involves amputation of the penis. This can be performed by amputation of the glans penis at the fornix and suturing of the prepuce to the urethral mucosa [11]; alternatively this can be performed at the perineal region, suturing urethral mucosa to the skin [5, 11]. Amputation of the glans penis at the fornix results in teaser bulls that experience pain during breeding attempts, thus decreasing libido and herd retention time [5]. With penectomy via the perineal approach, bulls often lose interest and experience decreased libido due to the