Читать книгу Bovine Reproduction - Группа авторов - Страница 221

The frenulum is a thin band of tissue found in juvenile bulls that extends from the midline of the ventrum of the tip of the penis to the attachment of the preputial epithelium near the base of the free portion. Like the epithelial connection between the penis and prepuce, this band of tissue normally separates under the influence of androgen exposure as the bull matures. Unlike the epithelial tissues joining the penis and prepuce, the 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.