Читать книгу Bovine Reproduction - Группа авторов - Страница 234

Pathologic spiral deviation of the penis occurs when the dorsal apical ligament slips laterally prior to intromission (Figure 15.14a). The role of the dorsal apical ligament in the development of spiral deviation is well described, but the factor or factors leading to the premature occurrence of this otherwise normal phenomenon are poorly understood [9, 30, 31]. Malfunction of the dorsal apical ligament due to a shortening of the ligament or lengthening of the penis as the bull ages was once commonly felt to be the cause but remains unproven. More recent speculation suggests that intravaginal spiral deviation occurs normally in many bulls, associated with peak erectile pressure, and that pathologic spiral formation occurs prematurely in bulls in which peak erectile pressure occurs prior to intromission. In either case, bulls with premature spiral deviation of the penis are unable to complete the copulatory act.

Figure 15.14 (a) Spiral deviation of the penis demonstrated during a test mating. (b) Spiral deviation of the penis induced with an electroejaculator during semen collection. Spiraling of the penis during electroejaculation is common and should not be confused with the pathologic deviation prior to achieving intromission shown in (a).

Source: Image courtesy of Clint Hilt.

A diagnosis of spiral deviation is suspected based on history and a description of the penis during the breeding attempt, but diagnosis can only be confirmed by an observed test mating. Because the penis of many normal bulls will spiral under the artificial stimulus of electroejaculation, diagnosis following observation of spiraling during stimulation with an electroejaculator is insufficient (Figure 15.14b). Deviation may be intermittent, especially early in the development of the condition, and repeated observations of test matings may be required to confirm the diagnosis.

No medical therapy is available to correct spiral deviation of the penis. Surgical correction of spiral deviation relies on induction of fibrous tissue to strengthen the attachments of the dorsal apical ligament to the penis. The available surgical techniques are described in Chapter 19. Spiral deviation is sometimes seen in association with damage to the dorsal nerves of the penis and careful observation at the time of test mating to rule out penile denervation should precede any attempted surgical correction.