Applied anatomy, pathophysiology and a revised scoring system of bull sheaths.

The sheath and prepuce are anatomically simple yet vital parts of the mating apparatus of the bull. They are also susceptible to a range of insults, and pathology of these structures is a common cause of infertility in both Bos taurus and Bos indicus bulls. Significant individual and breed-based variation occurs in the looseness of the skin, the presence and development of preputial muscles, the relative position of the opening to the cranial preputial muscles, the length of the prepuce, and the prominence of the umbilicus. Individual and breed-based susceptibility to different conditions is associated with these anatomical variations. Regardless of the cause, pathology of the prepuce generally results in sepsis, prolapse, stenosis or adhesions or a combination. Clinical examination should be aimed at determining the extent of these processes and the amount of healthy prepuce which would remain following successful treatment. The inclusion of evaluation of sheath conformation in the form of a sheath score is recommended. Current scoring systems do not reflect the diversity of predisposing factors to morbidity and may therefore fail to accurately reflect the risk of morbidity. A more detailed scoring system has been proposed. Further refinement of this system is outlined, consisting of a composite of scores for depth, umbilical skin fold, prepuce eversion, and distance from cranial muscle to opening (the 'Y' factor). Validation against actual bull performance is indicated to develop a valid and useful risk-management tool for use in evaluating sheath conformation.