frenulum often contains a large vein. When the process of normal separation fails, the frenulum may persist after breakdown of the other epithelial attachments and result in a band of epithelium and connective tissue joining the tip of the penis with the preputial epithelium at the junction of the prepuce and free portion of the penis (Figure 15.2). A persistent frenulum results in a sharp ventral bend of the distal penis as it becomes erect. Persistent frenulum is often detected in young bulls during a routine preservice breeding soundness examination [11], but occasionally is not detected until bulls attempt natural service.
Figure 15.2 Persistent frenulum. The presence of the persistent frenulum was noted at the time of a post‐purchase breeding soundness examination. A satisfactory pre‐purchase “semen test” had been provided at the time of sale, emphasizing the importance of examination of the external genitalia during a bull breeding soundness examination.
Source: Image courtesy of Dr. Clint Hilt.
The cause or causes of failure of separation of the preputial epithelium and/or frenulum are unknown. An unproven genetic association is suspected [12, 13]. Surgical transection of the frenulum is curative [13, 14], but limiting affected animals to use as terminal sires is recommended.
Injuries to the Prepuce
Bulls sometimes sustain injuries to the prepuce severe enough to interfere with breeding. Bulls from breeds with substantial Bos indicus influence have a pendulous sheath, excessive preputial skin, and a large preputial orifice, and bulls of this phenotype are predisposed to preputial trauma at the time of breeding. While Bos taurus breeds have less redundant skin in the area of the prepuce and are less likely to sustain breeding‐associated preputial trauma, preputial injury at the time of the ejaculatory lunge may occur in any breed.
Preputial Laceration
Bulls with a pendulous sheath and excessive preputial skin may traumatize the preputial tissues independent of the breeding act, but most serious preputial injuries occur at the time of the ejaculatory lunge. As the free portion of the penis enters the vagina during coitus, preputial skin slides caudally, up the shaft of the penis, toward the abdomen of the bull, and folds of redundant skin gather at the preputial orifice. This “bunching” of preputial skin usually occurs without incident, but when preputial tissue is inadvertently trapped between the abdomen of the bull and the bony pelvis of the female at the time of intromission, compressive forces generated at the time of the ejaculatory lunge can injure the entrapped tissues. With mild injury, the preputial epithelium remains intact and the accumulation of edema in the damaged tissues results in an uncomplicated preputial prolapse. More serious injuries result when compression of the entrapped prepuce disrupts the epithelium, with subsequent exposure and damage of the underlying elastic tissues. Commonly referred to as preputial laceration, the injury is in reality the result of bursting of preputial tissues in response to compressive force [15].
Preputial lacerations initiated during the breeding act are predictably located on the ventrum of the prepuce, with the initial disruption of the preputial tissues oriented longitudinally, parallel to the long axis of the bull's body. Following the injury, the disrupted tissues at the site of the injury become oriented transversely as the penis is retracted and the damaged preputial tissues are drawn toward the preputial orifice. As a result, the defect becomes oriented transversely (Figure 15.3). When the damaged preputial tissues cannot be retracted through the preputial orifice, the transverse orientation of the lacerated tissues results in shortening of the caudal aspect of the exposed prepuce and a characteristic “elephant trunk” appearance of the prolapsed tissues (Figure 15.4).
Figure 15.3 Preputial laceration in a breeding bull. The laceration assumed a transverse orientation as the preputial tissues were retracted toward the preputial orifice.
Figure 15.4 Preputial laceration with prolapse of the damaged preputial tissues. Reorientation of the wound results in the elephant trunk appearance of the prolapsed preputial tissue.
Trauma and disruption of the preputial epithelium and underlying elastic tissues is accompanied by inflammation and edema and the open wound inevitably becomes septic. As dependent edema accumulates, the prolapsed tissue increases in size and weight, and traction on the prepuce results in greater amounts of preputial tissue becoming exposed. Additional trauma, mutilation, and desiccation of the unprotected preputial tissues occur and wound contracture at the site of the injury distorts the tissues as the reoriented wound undergoes fibrosis and cicatrix formation (Figure 15.5).
Figure 15.5 Wound contracture and fibrosis at the site of a preputial laceration.
Source: Courtesy of Richard Hopper.
Preputial retractor muscles serve to elevate the prepuce and this elevation can minimize edema formation in damaged tissues. Many polled bulls lack retractor prepuce muscles and preputial prolapse following laceration in naturally hornless bulls tends to become more severe than similar injuries in horned animals [16].
Wolfe and Carson constructed a four‐point classification scheme that incorporates the severity of the preputial injury to estimate the prognosis for return to function and guide treatment decisions (Table 15.1) [17].
Table 15.1 Classification of preputial prolapse.
Source: Modified from [17], p. 258, © 1998, Wolters Kluwer.
| Category | Description | Treatment and prognosis |
|---|---|---|
| I | Simple preputial prolapse with slight to moderate edema without laceration, necrosis, or fibrosis | Either conservative or surgical treatment with good prognosis |
| II | The prolapsed prepuce has moderate to severe edema, may have superficial lacerations or slight necrosis, but has no evidence of fibrosis |
Surgery is the usual course of therapy with a good to guarded
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