Nature and cause of ocular dermoids were investigated by field studies, pedigree analysis, clinical examination and light microscopy. It was determined that ocular dermoids in cross-bred calves are genetically-transmitted defects. Calves typically were affected unilaterally or bilaterally with multiple, connected ocular growths that clinically and histologically mimicked normal haired skin. Sites most commonly involved included ventro-lateral limbus, third eyelid, medial canthus, eyelid and conjunctiva. Centro-corneal and anterior segmental dermoids were also observed. It is postulated from this study that bilateral ocular dermoids are genetically-transmitted defects in Hereford cattle. Characteristics of both autosomal recessive and polygenic inheritance were observed. However, mode of inheritance and role of environment in the pathogenesis of these peculiar and important developmental defects remain undefined. Extensive breeding trials utilizing superovulation, embryo transfer, and pre-terminal caesarean section as well as further field studies might be mandatory to confirm sex incidence, significance of associated somatic defects, role of environment in phenotypic expression, and mode of transmission of ocular dermoids in cross-bred calves.
Key words: Cross-bred calves, Dermoid cysts, Incidence, Ocular dermoids, Surgical intervention.