The Normal Morphology of the Bovine External Ear In Relation To Bovine Parasitic Otitis

Abstract

The normal morphology of the bovine external ear was studied in five Friesian/Boran crosses. This was undertaken to see if the anatomy of the area might have some influence in the development of parasitic otitis in cattle as there have been some claims that some cattle breeds have a long and tortuous external ear canal which might predispose the animals to the parasitic otitis.  It was found that the external ear canal was roughly round in cross section,  had a straight course and a slight upward incline from the horizontal plane. Unlike the outer two thirds of the canal, the inner one third had no skin like features. This lining, with its nonkeratinised epithelium whose cells appear to be loosely arranged and an almost absence of glands in the sub epithelium, has less protective qualities compared to that of the outer two thirds of the external ear. Such a lining would easily become infected after the slightest trauma. However, thf' superficial disposition of the vascular structures of the inner one third of the external ear allows for easy and faster access of defences to the epithelium in case of infections.