of Veterinary Medicine, Auburn University, Auburn, AL, USA
Introduction
Bulls commonly sustain injuries to the reproductive tract during natural breeding activity. Through close observation of their bull battery during the breeding season, cattle owners or managers can identify many reproductive tract maladies. Close observation of a cowherd during the breeding season can potentially reveal cows that are returning to estrus, a bull standing off to himself, or a swelling of and trauma to the external genitalia of a bull. All of these represent issues for further investigation or veterinary intervention, which in turn should lead to the identification of conditions such as penile hematoma, preputial prolapse, phimosis, paraphimosis, or an injury that has led to a denervation, vascular shunt, or deviation of the penis. Through the utilization of a bull breeding soundness examination (BBSE) prior to each breeding season, when properly performed as directed by the standards of the Society for Theriogenology, other problems such as fibropapillomas, hair rings, and minor preputial injuries can also be identified [1].
As all of the conditions that will be described in this chapter either hamper or potentially end the functional use of a bull, it is incumbent on our part to first correctly diagnose and then provide a reasonable prognosis for successful resolution. The prognosis obviously takes into consideration the severity of the injury or condition, but also the temperament of the bull, your facilities, and economics. The economic factors that must be considered include the replacement cost of the bull, his cull value, treatment costs, and service time lost for treatment and recovery.
Fibropapilloma
Fibropapilloma or warts are a common finding in young cattle under the age of 24 months. Caused by bovine papilloma virus, the virus is believed to enter the penile skin through wounds or abrasions sustained during homosexual activity among young bulls. The virus causes neoplastic growth of fibroblasts that is not locally invasive or metastatic. Often several bulls in a group will develop penile fibropapillomas and affected bulls frequently may not have obvious lesions on other parts of the body. Other neoplastic growth on the bovine penis is extremely rare [2]. Group housing of young bulls along with a predisposition for homosexual behavior both increase the incidence and add to the possibility that the penis will be among the affected locations. Penile warts (Figure 19.1) are usually identified at the time of a BBSE [3] or by an owner that notices a young bull that is reluctant or unable to breed. Bulls may present with either a phimosis or paraphimosis.
Figure 19.1 Penile fibropapilloma identified during routine BBSE.
Fibropapillomas may be managed by careful surgical removal with the bull restrained on a tilt table or in a squeeze chute [4], whether it be by excision, cryotherapy, or use of a laser, alone or in conjunction with immunization. Some level of prevention can be accomplished with the use of a commercial wart vaccine and it is my recommendation (Hopper) to administer wart vaccine to bulls following weaning that will be developed in large groups, specifically those to be shipped to bull test stations or to other group bull development stations where they will be housed with multiple bulls from multiple sources. When this is a continuous herd problem, utilization of an autogenous vaccine is a useful management tool [5].
Surgical removal begins with manually extending the penis and placing either a towel clamp under the dorsal apical ligament (Figure 19.2) or a gauze tourniquet around the penis proximal to the growth to aid in holding the extended penis. Prepare the surgical field and infiltrate 2–4 ml of 2% lidocaine subcutaneously across the dorsum of the penis proximal to the lesion (Figure 19.3). Repeat the surgical preparation and carefully identify the urethra to avoid incising this tissue during excision of the growth. Catheterize the urethra with a 10‐French male dog urinary catheter to help identify the urethra and thus avoid this structure (Figure 19.4). Then dissect the skin of the penis at the base of the lesion until the growth is completely removed. In lieu of sharp dissection with a scalpel, judicious dissection with a CO2 laser may assist hemorrhage control. Large growths are more easily removed by gradually debulking the lesion until the entire mass is removed. Ligate any small vessels and close the skin with #0 absorbable suture. Very small growths may be excised without anesthesia or suture closure. Remove the towel clamp and return the penis to the preputial cavity. Application of topical or systemic antimicrobials is optional.
Figure 19.2 Proper placement of towel clamp under dorsal apical ligament to hold penis in extension.
Figure 19.3 Subcutaneous injection of local anesthetic over dorsum of penis. This provides analgesia to distal penis.
Figure 19.4 Catheterization of urethra.
Penile fibropapilloma may recur if the bull is in an active state of the disease. Complete removal of the growth with an adjacent margin of unaffected penile surface epithelium lessens the likelihood of recurrence. In addition to the administration of a commercial or autogenous wart vaccine, anecdotal evidence suggests that the use of Immunoboost™ (Bioniche Animal Health, USA) may help prevent recurrence of penile lesions. Bulls treated for penile fibropapilloma should be examined for healing or regrowth four weeks following surgery before entering breeding service.
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.