Pizzle rot is an infection and inflammation of the prepuce that may lead to retention of urine and severe inflammation. It is seen mainly in wether sheep, especially if castrated at an early age. It is a less common and milder disease in rams, bucks and wether goats.
Most cases are in wethers coming from high protein pastures like clover or lucerne, or animals fed high protein pellets. The high protein intake results in concentrated urea in urine. Bacteria present in the urinary tract such as Corynebacterium renale produce an enzyme (urease), that breaks down the urea and releases ammonia. Ammonia is highly irritating to the mucous membranes lining the prepuce and the skin around the preputial opening, causing inflammation and ulceration.
Wethers are predisposed because they tend to have a short penis and often collect urine in the prepuce, resulting in continual wetting of the preputial opening and adjacent abdominal wool or hair. Other animals are predisposed if urine-soaked organic matter builds up in long hair or wool around the prepuce.
Clinical signs are usually advanced when noticed. There will be swelling, ulcers, scabs and a strong smell of ammonia at the opening of the prepuce. The first sign is a small ulcer on the skin at the tip of the pizzle. Scabs will develop over the ulcer. If scabs extend around the opening of the pizzle, passage of urine may be obstructed and allow infection and inflammation to extend deep into the prepuce and cause swelling. This may be confused with urolithiasis.
Non-progressive disease may occur in entire males as a small ulcer at the preputial opening of the sheath.
Remove wool around the area and clean and debride necrotic tissue. An incision along the bottom of the prepuce may be effective to drain accumulated pus and urine. This combined with a course of antibiotics (procaine penicillin, oxytetracycline, or trimethoprim sulpha) usually results in a rapid recovery.
During pre-export preparation, attention at shearing to remove hair and wool that might matt around the prepuce, and controlling dietary protein will be effective.