Onset and Stages of Osteogenesis in the Rabbit (Oryctolagus cuniculus) using Diaphonisation

BACKGROUND: Developmental anatomy is a prerequisite for a real understanding of gross anatomy and teratol-ogy. It is concerned with the sequential stages of embryonic and fetal development, beginning with fertilization. Moreover, it helps to describe developmental changes and abnormalities, heredity, sexing, and the appearance of vestigial structures. Powerful advancements in molecular genetic manipulation and assisted reproductive technolo-gies are employed during embryo and fetal development, and these efforts have had profound impact on animal production worldwide. OBJECTIVES: The present study was carried out to investigate the onset and stages of osteogenesis in rabbit (Oryctolagus cuniculus). METHODS: Forty mature rabbits (33 does and 7 bucks) with a mean weight of 2 kg were included in this study. They mated twice at a ratio of three does to one buck on day zero (0). Mounting was carefully observed to ensure mating occurred and was confirmed by the physical examination of the vulva for swelling and redness, while preg-nancy diagnosis was confirmed by ultrasonography and abdominal palpation. Embryos and fetuses were extracted via a ventral incision on the abdominal and uterine walls of one pregnant doe each day after euthanization with thiopental sodium at the dose of 31 mg/kg body weight intravenously. Diaphonisation was employed in studying osteogenesis. RESULTS: Osteogenesis began at fetal day 21 (F21) using diaphonisation. In the skull, the bones of the splanchnocranium appeared before the neurocranium. The centrum and transverse processes were the first identifi-able features of all different types of bone in the vertebral column to be ossified. The spinous process and the fusion of the sacrum and sternum were not detected throughout the gestation period. It was also observed that the epiphys-eal and articular ends of none of the bones, neither in the fore nor hind limbs were ossified throughout gestation. Specifically, while the primary ossification centers of the middle phalanges were the last to appear in the manus and pes, all the carpals were absent, and only the calcaneous was evident in the tarsal bones. CONCLUSIONS: We recorded the onset of osteogenesis and subsequent development throughout the gestation period of rabbits, which has added some valuable information to the documented literature on the bone development of this species.