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Physiological Examination of Ratite Orthopedic Disorders and Soft‐Tissue Visualization via Micro‐CT

Many hard‐tissue (e.g., bone, dentine, enamel) pathologies directly impact the development and function of soft‐tissue structures. Such pathologies can be unique to captive individuals and tend to be more common among large‐bodied captives such as crocodilians, elephants, and flightless birds. Emus (Dromaius novaehollandiae) are large‐bodied flightless birds that are uniquely efficient at both anaerobic sprinting and aerobic, sustained running. Native to Australia, they are commonly farmed in North America for oil and meat, but growth of the emu industry has been hampered by poorly understood orthopedic disease states (i.e., splayed‐leg disorder). Few studies have examined captive emu skeletal muscle, and none have documented the enzymatic profile of ratite cardiac tissue. We sought to bridge this gap by providing a quantified understanding of physical degradation in this large farm‐raised species. Surprisingly, we found the metabolic profile of captive emu cardiac tissue to be most similar to that of active, flying birds. Additionally, metabolic baselines for primary locomotor muscles between splayed and non‐splayed limbs indicate enhanced metabolic enzyme activities and myoglobin levels, resulting in a distinctly more “athletic” phenotype than control limbs. This compensatory increase in aerobic capacity demonstrates how soft tissues can mitigate functional issues caused by pathologies and suggests that muscle atrophy does not contribute to splayed‐leg disorder. Likely, other factors are to blame (e.g., nutrition). With the advent of more detailed imaging techniques, such as contrast‐enhanced micro‐CT imaging, we hope to test for signal of these factors and better understand the anatomy and physiology of health and disease states in ratite birds. Through documentation of the interplay between hard and soft structures, including their physiologies, we are now beginning to apply new tools to an ancient clade of poorly‐understood birds.