The sensoneural organization of the snout skin of the cow (Bos indicus) in light of the somatosensory adaptations of mammals

Background: In bovines, snout is used as a tactile organ while foraging for food and in social interaction. The snout has the surface that is comparable to the glabrous skin of most non-hooved mammals. Aim of study: To study the structure, pattern of innervation and nerve terminations in the snout of the cow, so as to understand somatosensory adaptation of mammals. Material and Methods: Skin samples from fifteen animals (cow/ox) were taken, sections prepared and stained with a cytological (Haematoxylin – Eosin and Von Gieson’s stains) and a neural stain (Silver Impregnation). Results: With cytological stain, the bovine snout consisted of glabrous skin having well defined dermal ridges. Three types of cells were seen in the epidermis- keratinocytes, melonocytes and Merkel’s cells. After silver impregnation, nerve plexuses were observed in the dermis, from which myelinated nerve fibers ascended up towards epidermis. Four types of nerve fibers were observed in the snout: free nerve endings, Merkel’s nerve endings, papillary nerves and bovine corpuscles. Free nerve endings were sparse due to their loss to tactile friction i. e. grazing. Merkel’s cells were grouped at the dermal pegs. The bovine corpuscular nerve endings, present in the dermal papillae, were two types: one was elongated or cylindrical and the other oval or globular, formed high up in the dermal papilla, close to stratum granulosum. Both types consisted of capsule formed of collagen fibers and capsular cell; surrounding inner core formed by ramifying afferent nerve fibers, Schwann/lamellar cells and collagen fibers. The terminal nerve fibers of the bovine corpuscles formed modifications like neurofibrillar networks, closed end bulbs and neuro fibrillar varicosities. Conclusion: Snout of the cow possess the tripartite array of nerve end organs associated with Eimer’s organ of mammals, consisting of free nerve endings, Merkel’s discs and corpuscular end organs, which indicates that the snout is a highly specialized somatosensory organ of bovine animals.