Bovine Reproduction. Группа авторов
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Hair Ring
Although far less common than warts, the presence of a hair ring also occurs due to homosexual behavior and group housing of young bulls. Accumulation of hair during riding and the continuous action of riding with extension and retraction of the penis serve to create a tight band of hair (Figure 19.5). Hair rings are typically identified during a BBSE and treatment is simply removal and application of a suitable ointment. Because the encircling ring may become sufficiently tight to cause pressure necrosis with damage to the urethra, careful examination to determine the depth of the lesion is warranted [6]. Small urethral fistulae will typically heal on their own, but those that are larger and more proximally located must be closed (Figure 19.6). In severe cases the constricting ring may cause avascular necrosis to the extent that damage to the dorsal nerves of the penis or sloughing of the entire glans penis can occur.
Figure 19.5 Penile hair ring.
Figure 19.6 Urethral fistula that is of a size and location to require repair.
Persistent Frenulum: Delayed Preputial–Penile Separation
The penis of the bull calf cannot be extended prior to puberty due to the interdigitating attachment of the skin of the penis and prepuce and the lack of a sigmoid flexure. During puberty, androgen production shifts from androstenedione to testosterone, and the attachment of the penis and prepuce begins and should be complete between 8 and 11 months of age. Occasionally, young bulls between the age of 12 and 14 months will present with incomplete separation [4, 7]. In these bulls separation can be completed by pulling the prepuce back from the free portion of the penis. These tissues should separate easily and hemorrhage is seldom a problem.
The penile frenulum is a thin band of connective tissue on the ventral midline of the free portion of the penis, which adjoins the prepuce. Normally the frenulum ruptures during penile separation from the prepuce. When the frenulum does not rupture, the penis extends but the frenulum causes ventral bending of the distal penis during extension (Figures 19.7–19.9). Surgical repair is relatively simple. I recommend ligating each end of the frenulum and transecting the tissue to reduce the possibility of hemorrhage, although not all practitioners adhere to this practice (Figures 19.10–19.12). The owner should be advised that this condition is considered to be heritable and retaining the bull's sons as sires is not recommended.
Figure 19.7 Persistent frenulum preventing complete straightening of erect penis.
Figure 19.8 Persistent frenulum with two branches attached from prepuce to penis.
Figure 19.9 Very short persistent frenulum preventing separation of penis and prepuce.
Figure 19.10 Transfixation ligatures on each end of persistent frenulum.
Figure 19.11 Excision of frenulum adjacent to transfixation ligatures.
Figure 19.12 Completed excision of frenulum.
Preputial Injury
Bulls most commonly sustain injuries to the prepuce during breeding. The extent of disruption of the surface epithelium and peri‐penile elastic tissue determines the prognosis and therapeutic approach for returning the bull to breeding soundness. The veterinarian should understand the etiology of preputial injury and the therapeutic options for the animal [4, 6].
Primary preputial prolapse in the bull is usually a sequela to breeding injury, frostbite, or balanoposthitis caused by herpesvirus infection (infectious bovine rhinotracheitis/infectious pustular vulvovaginitis, or IBR‐IPV). Secondary preputial prolapse is often seen with penile hematoma or urethral rupture. Bulls suffering preputial frostbite may undergo considerable necrosis of the preputial epithelium and heal with mild to severe preputial stenosis (Figure 19.13). IBR‐IPV most commonly affects young bulls and the prepuce may be extremely edematous, with vesicles or pustules on the preputial epithelium. These bulls usually respond well to sexual rest, application of emollient ointments, and conservative therapy, which may include hydrotherapy and support bandaging.
Figure 19.13 Severe preputial stenosis due to frostbite.
Laceration of the prepuce of Bos taurus breeds usually does not lead to preputial prolapse. The damaged prepuce is typically withdrawn into the sheath and swelling of the sheath may or may not be observable. Minor injuries are often unnoticed, heal without complication, and result in only minor superficial scarring [4,6–9]. However, it should be noted that occasionally the resultant scar tissue will create pain during breeding [1]. In this case a scar revision procedure can be utilized. Some B. taurus bulls with preputial laceration develop paraphimosis, where the damaged tissues will not allow retraction of the penis into the sheath (Figure 19.14). Alternatively, some bulls that do retract the penis into the sheath develop phimosis due to stricture of the injured prepuce (Figures