Cassowary pediatrics.

Abduction at the stifle joint is a common deformity upon hatching often referred to as splay leg. One possible cause hypothesized is larger yolk sacs force apart the cassowary chick's legs (see Fig. 17). Splay leg is most common in the first 2 or 3 chicks of the season. Usually 1 leg is affected but both can be involved. Treatment is generally successful with bandaging techniques. This is done by hobbling with bandage tape. (above the hock) for 3 days and observing closely for correct alignment.

Osteoinductivity of partially purified bovine, ostrich and emu bone morphogenetic proteins in vitro.

The aim of this study was to observe the osteogenic activity of native bone morphogenetic proteins (BMPs) obtained from different species including bovine, ostrich and emu sources in order to compare mammalian and avian BMPs. Rat mesenchymal progenitor marrow stromal cells and pre-osteoblastic C2C12 cell cultures, were exposed to the native BMPs and alkaline phosphatase (ALP) and creatine kinase (CK) levels were determined by assay. The results showed that the ALP activity in C2C12 cultures was elevated by bovine BMP by 2- to 10-fold (p < 0.05-0.001) from day 3 during 14 days. There were no significant differences in avian BMP related elevations of ALP activity except with ostrich BMPs at day 14 (p < 0.05). However, exposure of MSCs cultures to BMPs derived from bovine, ostrich or emu sources resulted in elevated ALP from day 3 (p < 0.05). Bovine BMP resulted in more ALP elevation than with either of the avian BMPs. All of BMPs elevated Creatine kinase (CK) activity from day 1 and climbed until peaking at day 7. Compared with control cultures, CK was elevated more with exposure to emu BMP and was more elevated with greater statistical significance than with bovine and ostrich BMP before day 5. These higher levels remained until day 14 (p < 0.05). The results of this study suggest that both bovine and avian BMPs are able to stimulate osteogenesis in mature osteoblasts in vitro. The strongest synergistic effect on osteogenesis was detected in cells stimulated with bovine BMP. Avian BMPs had lower effects on ALP and CK activity, emu BMP being more effective than ostrich BMP.

Skeletal strain patterns and growth in the emu hindlimb during ontogeny.

Most studies examining changes in mechanical performance in animals across size have typically focused on inter-specific comparisons across large size ranges. Scale effects, however, can also have important consequences in vertebrates as they increase in size and mass during ontogeny. The goal of this study was to examine how growth and development in the emu (Dromaius novaehollandiae) hindlimb skeleton reflects the demands placed upon it by ontogenetic changes in locomotor mechanics and body mass. Bone strain patterns in the femur and tibiotarsus (TBT) were related to ontogenetic changes in limb kinematics, ground reaction forces, and ontogenetic scaling patterns of the cross-sectional bone geometry, curvature and mineral ash content over a 4.4-fold increase in leg length and 65-fold increase in mass. Although the distribution of principal and axial strains remained similar in both bones over the ontogenetic size range examined, principal strains on the cranial femur and caudal femur and TBT increased significantly during growth. The ontogenetic increase in principal strains in these bones was likely caused by isometry or only slight positive allometry in bone cross-sectional geometry during growth, while relative limb loading remained similar. The growth-related increase in bone strain magnitude was likely mitigated by increased bone mineralization and decreased curvature. Throughout most of ontogeny, shear strains dominated loading in both bones. This was reflected in the nearly circular cross-sectional geometry of the femur and TBT, suggesting selection for resistance to high torsional loads, as opposed to the more eccentric cross-sectional geometries often associated with the bending common to tetrapods with parasagittal limb orientations, for which in vivo bone strains have typically been measured to date.

In vivo bone strain and ontogenetic growth patterns in relation to life-history strategies and performance in two vertebrate taxa: goats and emu.

This study examined ontogenetic patterns of limb loading, bone strains, and relative changes in bone geometry to explore the relationship between in vivo mechanics and size-related changes in the limb skeleton of two vertebrate taxa. Despite maintaining similar relative limb loads during ontogeny, bone strain magnitudes in the goat radius and emu tibiotarsus generally increased. However, while the strain increases in the emu tibiotarsus were mostly insignificant, strains within the radii of adult goats were two to four times greater than in young goats. The disparity between ontogenetic strain increases in these taxa resulted from differences in ontogenetic scaling patterns of the cross-sectional bone geometry. While the cross-sectional and second moments of area scaled with negative allometry in the goat radius, these measures were not significantly different from isometry in the emu tibiotarsus. Although the juveniles of both taxa exhibited lower strains and higher safety factors than the adults, the radii of the young goats were more robust relative to the adult goats than were the tibiotarsi of the young compared with adult emu. Differences in ontogenetic growth and strain patterns in the limb bones examined likely result from different threat avoidance strategies and selection pressures in the juveniles of these two taxa.

Cardiac rhythms in developing emu hatchlings.

Six emu hatchlings were non-invasively measured for electrocardiogram (ECG) from their chest wall using flexible electrodes, and the instantaneous heart rate (IHR) was determined from ECG throughout the first week of post-hatching life. Although the baseline heart rate (HR) was low, approximately 100-200 beats per min (bpm), compared with chick hatchlings, the IHR fluctuated markedly. The fluctuation of IHR comprised HR variability and irregularities that were designated as types I, II and III in chick hatchlings and additional large accelerations distinctive of emu hatchlings. Type I was HR oscillation with a mean frequency of 0.37 Hz (range 0.2-0.7 Hz), i.e. respiratory sinus arrhythmia (RSA). From RSA, breathing frequency in emu hatchlings was estimated to be approximately half of that in chickens. Type II HR oscillation was also found in the emu; the frequency ranged from approximately 0.04 to 0.1 with a mean of 0.06 Hz, and the magnitude tended to be large compared with that of chickens. In addition to type III HRI, which was designated in chickens, large, irregular HR accelerations were characteristic of emu hatchlings. From IHR data, developmental patterns of mean heart rate (MHR) were constructed and plotted on a single graph to inspect the diurnal rhythm of MHR by visual inspection and power spectrum analysis. A circadian rhythm was not clear in the emu hatchlings, in contrast to chick hatchlings, which showed a dominant diurnal rhythm.

Plasma thyroid hormones and growth hormone in embryonic and growing emus (Dromaius novaehollandiae).

Growth hormone (GH), thyroxine (T4) and tri-iodothyronine (T3) are known to be involved in the regulation of growth and development in a variety of avian species. It has been suggested that an absence of GH and thyroid hormones in ostriches is the cause of their neoteny, a phenomenon in which juvenile characteristics are retained into adulthood. Neoteny is typical of all ratites, the single group of flightless birds that includes the ostrich, but similar endocrine studies have not been performed for other members of the group, such as the emu. To test the neoteny hypothesis further, in the present study we measured the plasma concentrations of T4, T3 and GH in emus during embryonic development and from hatching to 1 year of age. Concentrations of T4 and GH increased during the last weeks of incubation, whereas concentrations of T3 were highly variable. After hatching, the concentrations of both thyroid hormones were high during the first 3 days of life and then fell to a constant low level. Plasma concentrations of GH were high at the time of hatching and decreased gradually over the first 22 weeks of age; thereafter, the concentrations of GH were highly variable. No correlation was observed between hormone concentrations and live weight at any time. These results support the hypothesis that thyroid function is abnormally low in ratites, whereas patterns of GH secretion are similar to those observed in other birds. Dysfunction of the thyroid axis could explain, in part, the neotenous physical aspect of adult emus.

Periosteal bone growth rates in extant ratites (ostriche and emu). Implications for assessing growth in dinosaurs.

The first quantitative experimental data on growth dynamics of the primary cortical bone of young ratites demonstrate the following. 1) From hatching to 2 months of age, cortical thickness remains constant, thereby expressing equilibrium between periosteal bone deposition and an endosteal bone resorption. 2) Radial growth rates of the diaphyseal bone cortex are high (10-40 microns.day-1 on average--maximum 80 microns.day-1) in the hindlimb (femur, tibiotarsus and tarsometatarsus). Wing bones are smaller and later developed. They have lower rates of radial osteogenesis (2-14 microns.day-1). 3) High growth rates are linked to densely vascularized primary bone belonging to the reticular or laminar tissue types. Growth rates fall when bone vascular density decreases. These results emphasize the importance of examining a large number of skeletal elements in order to build a precise knowledge of the general relationship between bone growth rate and bone tissue type. They also stress the potential of bone growth rate quantification among extinct tetrapods, including non-avian dinosaurs.

Lysine requirements of growing emus.

1. The lysine requirement of growing emus between 23 and 65 d of age was determined according to growth response variables. 2. The optimal lysine requirement of emus was found to be 0.83 and 0.90 g/MJ ME for growth rate and gain:food ratio respectively. These findings are in accordance with the recommended value of 0.80 g/MJ ME, but is lower than the recommended value for ostriches (1.02 g/MJ ME) and higher than determined values for broilers (0.75 g/MJ ME) of the same age range.