Serum lipid reference intervals of high-density and low-density lipoprotein cholesterols and their association with atherosclerosis and other factors in Psittaciformes

The prevalence of atherosclerosis is high in captive psittacine populations and the disease and subsequent heart problems have become a common reason for consultations in avian veterinary practices. To this day, ante-mortem diagnosis in birds remains challenging, however the serum lipoprotein-panel has been suggested to potentially aid in the diagnosis of the disease and provide better understanding of the pathogenesis. In parrots, unlike in humans, an association between serum lipoproteins and atherosclerosis has not been proven so far. The present retrospective cohort study aimed to establish multi-genera serum reference intervals for high-density-lipoprotein cholesterol (HDL-C) and low-density-lipoprotein cholesterol (LDL-C) in various parrot species. In addition, an evaluation on the changes of HDL-C and LDL-C depending on intrinsic and extrinsic factors of genus, age, sex, diet, prevalence of atherosclerosis, reproductive activity and body condition score was performed. An analysis of 1199 blood samples originating from 694 birds of multiple parrot genera revealed genus-specific variations in lipoprotein levels. Lipoproteins were studied for their association with independent variables of diet, age, sex, reproductive and breeding status, atherosclerosis and body conditioning score. A significant association between LDL-C levels and the prevalence of atherosclerosis could be observed, similar to findings in humans. Diet was found to be influencing both lipoprotein levels and risk for the development of atherosclerotic disease. Results showed, that LDL-C appears to be a potential predictor of atherosclerosis, while the role of HDL-C remained less conclusively defined. The results of the study provide a foundational framework for the future use of lipoprotein analysis in parrot medicine, offering novel insights into the management of cardiovascular health in pet parrots.