Histological examination of the antlerogenic region of red deer (Cervus elaphus) hummels.

Hummels are antlerless red deer stags. This abnormality has been attributed to poor feeding conditions which result in failure by the deer to grow complete pedicles. Incomplete pedicles lack the potential to develop normal antlers. The histological examinations in this study showed that the rudimentary pedicles (5 mm and 15 mm in height) grown by the two hummels respectively were developed by intramembranous ossification. This is the way that the frontal lateral crests of normal deer are formed, while, in contrast, antlers grow by endochondral ossification. The transition between the ossification types is most important, and occurs during pedicle growth. Therefore, we suggest that the antlerless condition of hummels is due to their failure to initiate true pedicle growth (which has the potential to develop into an antler) because the change from one ossification type to another does not occur. In view of the fact that both hummels were very small in terms of weight (33.7 kg and 51.8 kg, respectively) for their age, it is possible that nutritional cues are necessary for complete pedicle formation. Presumably these cues act synergistically with androgens for the development of the pedicle/antler as a secondary sexual character. It is possible that nutrition controls pedicle initiation through the IGF1 pathway.