The mechanism of antler casting in the fallow deer

Abstract

The process by which antlers are detached from their pedicles was examined histologically in fallow deer castrated in the autumn to induce precocious casting. Osteoclastic erosion across an abscission line between the dead bone of the antler and the living bone of the pedicle was found to be responsible for the separation of the 2. As early as 3 days after castration, osteoclasts and associated lacunae were present on the sides of the pedicle bone. These were then found in progressively deeper locations, by 2 weeks extending across the entire width of the pedicle. Concomitant with the centripetal spread of osteoclasts was the enlargement of Haversian canals, the surfaces of which became lined with osteoclasts. These widening vascular channels within the bone were filled with connective tissue, which in precasting stages formed a mesodermal pad about 1 mm thick. In later stages, a circumferential cleft was excavated beneath the antler burr, and connective tissues from the surrounding pedicle skin invaded the space between the antler and pedicle. After casting, the ingrowing integumental tissues fused with the mesodermal tissues derived from the vascular channels of the pedicle to give rise to an incipient antler bud beneath the scab. The ingrowth of epidermis capable of de novo hair follicle formation gave rise to the future velvet skin that envelops the elongating antler.

Histological structure of antlers in castrated male fallow deer (Dama dama)

“…Castration of male deer carrying hard antlers as well as the administration of substances interfering with testosterone production or inhibiting both testosterone production and its action at the receptor level causes premature antler casting (Wislocki et al, 1947;Lincoln, 1971;Muir et al, 1982;Jaczewski, 1985;Bubenik GA et al, 1987, 2002Goss et al, 1992;Schams et al, 1992;Kierdorf U et al, 1993Suttie et al, 1995). Administration of testosterone or estradiol to males in hard antler postpones antler casting beyond the normal date (Goss, 1968).…”

Deer Antlers – A Model of Mammalian Appendage Regeneration: An Extensive Review

“…During typical skin wound healing in adult mammals, the initially formed granulation tissue is transformed into the scar tissue [46,48] . A capillary-rich fibrocellular tissue resembling granulation tissue has also been reported to occur between the pedicle bone and the scab during casting wound healing [39,41,42] . The fate of this tissue has not been studied so far, but it is assumed that if a scar is formed during antler regeneration it is derived from it.…”

“…Antler casting is preceded by osteoclastic activity that is most intense in a narrow zone of the distal pedicle corresponding to the future separation plane [33,39] . Bone resorption occurs both within the pedicle and at its surface [33,39,40] .…”

“…Bone resorption occurs both within the pedicle and at its surface [33,39,40] . Typically, the antler plus a small portion of the most distal pedicle bone breaks away from the pedicle before all connections between the two parts have been eroded.…”

“…This basal lamina is established in peripheral areas of the healing casting wound at a time when epithelialization of the more central wound areas has not yet been completed [13,15] . Histological studies further showed that the epidermal ingrowth is accompanied by that of the dermis so that, within a matter of days, the casting wound area is overlain by a layer of skin rather than just a wound epidermis [39,42] .…”