Diseases of the Reproductive System of the Bull

CHAPTER 32 Diseases of the Reproductive System of the Bull



Conception failure may be associated with female factors, male factors, or both. Too often, it is assumed that infertility is a female problem, and few bulls are examined for breeding soundness before the breeding season. Most bulls are examined because of reproductive failure discovered during or after the breeding season. Estimates of the proportion of bulls having significant reproductive problems range from 5% to 25%. Very often the most cost-effective way of dealing with reproductive diseases of the bull is culling and replacement.



COMMON PENILE PROBLEMS


The lesions of penile fibropapillomatosis are warts. Fibropapillomas are the most common mass seen on the bull’s penis and have a viral etiology. The causative virus is believed to gain entry into the preputial epithelium through abrasions of the penis associated with mating activity among bulls. This problem usually is seen only in young bulls and is not associated with warts on other parts of the body.


Clinical signs may not be evident in penile fibropapillomatosis, and the problem may be recognized only during a breeding soundness evaluation. Bleeding from the preputial opening may be seen, along with reluctance to mate. Phimosis or paraphimosis may result from the presence of larger masses.


Penile fibropapillomas may occur as single or multiple masses. The mass usually is pedunculated, but sessile lesions with a diffuse distribution also are possible.


Fibropapillomas sometimes will regress without treatment. Surgical removal of pedunculated masses is straightforward. Commercial wart vaccine has been used in treatment, with variable results. Commercial autogenous wart vaccine may be more useful in preventing recurrence of the problem, which may occur in up to one third of affected animals.


Persistent penile frenulum is a congenital band of tissue extending from the median raphe of the prepuce to the ventral side of the penis near the glans. Penile erection and extension in affected animals results in a ventral bowing of the penis. In bulls with longer prepuces, the prepuce may be pulled over the glans penis by the band. In either case, successful intromission is unlikely. This condition is believed to be heritable, and affected animals should be used only as terminal sires.


Surgical correction of persistent penile frenulum requires that the penis be extended and secured. Local anesthetic injection is given at each end of the band. Blood vessels and the band are ligated, and the band is transected and removed. Healing occurs rapidly.


Inflammation of the penis and prepuce occurs occasionally in younger bulls. Pain resulting from this inflammation may be severe enough that the affected bull mates less often or not at all. Most frequently, this condition is associated with abrasions occurring at mating or infection with bovine herpesvirus type 1 (BHV-1) (i.e., infectious bovine rhinotracheitis–bovine virus diarrhea [IBR-BVD]). BHV-1 infection causes small areas of focal necrosis, resulting in 1- to 3-mm-diameter ulcers. Inflammation of the penis and prepuce may be severe enough to produce adhesions, with limitation of future fertility. In most cases, however, the problem is self-limited and will resolve after 2 weeks of sexual rest.


Hair rings encircling the penis may be seen, especially in younger bulls that are housed in groups. It is believed that these hair rings result from mating activity during which the penis is rubbed across loose body hair. Eventually, a ring of hair may accumulate on the penis, resulting in discomfort, necrosis, and occasionally, urethral fistula or penile amputation. Removal of the hair ring and local wound therapy should result in the resolution of reversible pathologic changes.



DISEASES OF ACCESSORY SEX GLANDS


The most commonly recognized disease of the internal genitalia of the bulls is vesiculitis. Inflammation of the vesicular glands most frequently is diagnosed in bulls younger than 2 years of age or older than 9 years. The incidence of vesiculitis usually is low but can be quite high in some groups of young bulls. Inflammation of other parts of the reproductive system often is seen with vesiculitis. The effect of vesiculitis on fertility is variable. Although it is not uncommon for no infectious agent to be identified as the cause of vesiculitis, a number of bacteria and viruses have been associated with this problem. Brucella abortus, Arcanobacter pyogenes, Haemophilus somnus, and others have been described as bacterial causes of vesiculitis. The IBR virus and enteroviruses have been incriminated.


The pathogenesis of vesiculitis has not been clearly established. A number of risk factors for this condition have been reported. Young bulls that are housed in contained groups and fed high-energy rations seem to be more susceptible. Slaughterhouse studies have shown an association between vesiculitis and other infectious diseases such as pneumonia, liver abscesses, and navel ill.


Most affected bulls do not show visible signs of vesiculitis. Occasionally, signs of abdominal pain or rear leg lameness may be noted. More often, this disease is diagnosed during a routine breeding soundness evaluation or during examination of the bull as a part of a herd infertility investigation.


Considerable variation in vesicular gland size, consistency, and texture is normal in bulls. Consequently, the interpretation of findings on rectal examination may be difficult. Inflamed vesicular glands are enlarged, painful, and firm. Loss of lobulations may be noted. The vesicular glands may be adherent to adjacent structures. Abscessation can occur. Changes may be unilateral or bilateral. The ejaculate of affected animals may be darker than normal in color and contain clumps. Microscopic examination characteristically reveals an increased number of polymorphonuclear cells. These cells cannot be identified using the usual eosin-nigrosin sperm stain, and a white blood cell stain is necessary. Sperm motility generally is lower in affected bulls.


Bulls older than 9 years of age seldom recover from vesiculitis. Usually, these bulls are culled. Bulls younger than 2 years often recover within 6 months with no treatment at all. Medical treatment of this condition is based on long-term antibiotic therapy. The culture of routinely obtained semen samples is not useful, because gross contamination is the rule. A procedure for the collection of fluid for culture has been described. After cleansing of the ventral abdomen, the penis of a suitably tranquilized bull is extended and secured. A catheter is passed up the urethra and fluid is collected during rectal massage. Even with favorable laboratory results, treatment with appropriate antibiotics often is disappointing. Treated bulls often improve during treatment, only to relapse after the course of therapy is complete. Macrolide antibiotics and flunixin often have been recommended for cases of seminal vesiculitis. Surgical removal of diseased glands is difficult, but a newly described ventral pararectal approach shows promise. Culling of affected bulls probably is the most cost-effective approach. It has been reported that the incidence of vesiculitis in high-risk groups has been reduced by feeding of chlortetracycline.

Sep 3, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Diseases of the Reproductive System of the Bull
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