Vet Advice

The bulls are out on pasture and we now have time to consider one of the bull problems we encountered this spring. Seminal vesiculitis is the most common abnormality detected on rectal examination during breeding soundness examinations on yearling bulls and, much less commonly, in older bulls. Many of these bulls would have shown no indication of a problem.

The seminal vesicles are the major accessory sex glands in the bull and function as the main source of seminal fluid. They are paired structures that lie on the floor of the pelvis and are connected to the urethra by a small duct. The size varies between individuals and the glands may be asymmetrical. The veterinarian would have palpated the seminal vesicles and may have found excessive size, firmness and / or loss of lobulation and increased sensitivity indicating that this bull has or had a problem

On collection of the semen, purulent material in the ejaculate may easily been seen as copious amounts of thick stringy, slimy material or the ejaculate may appear normal until the semen slide is evaluated under the microscope. The diagnosis is made, treatment is recommended and a prognosis is discussed using both the physical findings and the microscopic findings.

Seminal vesiculitis occurs on average in two to four per cent of yearling bulls but the incidence varies greatly from farm to farm and year to year. Yearling bulls are more prone to this problem for a variety of possible reasons. Young bulls may not have had time to develop immunity to the virus and/or bacteria causing the problem. Bulls in groups where riding is occurring may also be predisposed. Nutrition of the young bull may play a role, as does stress.

The pathogenesis (or how the disease begins) is not completely understood. Infection entering the gland by coming up the urethra is probably not the main mechanism.The infection may descend from the testes, epididymides or related structures. The organisms are most likely carried to the glands by the blood (septicemia) during a naval infection, chronic pneumonia, kidney infection, arthritis or foot rot -- a previous problem where bacteria have entered the blood from another site. Bulls on a high energy diet can have a ruminitis or inflammation of the rumen wall and organisms can enter the blood going to the vesicles or forming liver abscesses which act as a shedding site.

The course of the disease is highly variable. Usually there is an inflammatory response with invasion by bacteria. Spontaneous remission can occur or the bull can become chronic with scarring and pockets of purulent material with possible involvement of adjacent structures.

The prognosis and response to treatment is also highly variable. If the disease is detected during an early stage antibiotics may be useful. Culture and sensitivity on the semen will help to ensure and appropriate antibiotic will be used. Identification of the organism may help determine the source of the infection. Your veterinarian may have suggested a culture and sensitivity. She may have discussed forwarding these results as well as information about your bull and subsequent finding to a vesiculitis study being undertaken at the Western College of Veterinary Medicine. The study is attempting to address the gaps in the knowledge of this problem so veterinarians can better advise producers on how to control this problem.

We do know that spreading out the bulls, reducing stress and feeding an appropriate diet should decrease the incidence. Ensure that a healthy calf born from a healthy vaccinated cow receives adequate colostrum to reduce the incidence of naval infection, scours and pneumonia. When a calf does become ill treat the calf early with the appropriate antibiotic at the right dose by the right route for long enough to eliminate the disease.

If you are faced with a number of these cases in your yearling bulls, do a diagnostic workup on the semen and review the history of these animal with your veterinarian to develop a strategy to reduce the problem in the future.