Beyond the Chicken: Alternative Avian Models for Developmental Physiological Research

Abstract

Biomedical research focusing on physiological, morphological, behavioral, and other aspects of development has long depended upon the chicken (Gallus gallus domesticus) as a key animal model that is presumed to be typical of birds and generally applicable to mammals. Yet, the modern chicken in its many forms is the result of artificial selection more intense than almost any other domesticated animal. A consequence of great variation in genotype and phenotype is that some breeds have inherent aberrant physiological and morphological traits that may show up relatively early in development (e.g., hypertension, hyperglycemia, and limb defects in the broiler chickens). While such traits can be useful as models of specific diseases, this high degree of specialization can color general experimental results and affect their translational value. Against this background, in this review we first consider the characteristics that make an animal model attractive for developmental research (e.g., accessibility, ease of rearing, size, fecundity, development rates, genetic variation, etc.). We then explore opportunities presented by the embryo to adult continuum of alternative bird models, including quail, ratites, songbirds, birds of prey, and corvids. We conclude by indicating that expanding developmental studies beyond the chicken model to include additional avian groups will both validate the chicken model as well as potentially identify even more suitable avian models for answering questions applicable to both basic biology and the human condition.

Physiological Regulation of Growth, Hematology and Blood Gases in Chicken Embryos in Response to Low and High Incubation Humidity

“…In contrast, there were no differences in hatchability among eggs incubated at ∼40–70% RH ( Buhr, 1995 ) and, similarly, in our study mean hatchability was unaffected by Low or High RH. There are clear physiological differences between different strains of chickens ( Flores-Santin and Burggren, 2021 ) and these differences may extend back to the embryo, perhaps accounting for hatching variability in different relative humidities. Further experiments are required to determine the mechanisms underlying humidity-affected hatchling success.…”

Domestication and the comparative embryology of birds

“…The taxonomic breadth of avian species sampled in comparative embryological studies warrants expansion (Flores-Santin et al, 2021), though this may prove challenging owing to conservation concerns and variable life history characteristics of species. Nonetheless, the stages for chicken embryos of Hamburger and Hamilton (1951) were recently used as reference points to statistically predict (using regression models) the duration of developmental phases in diverse species in which data for the corresponding developmental characters were missing (Cooney et al, 2020).…”

Experimental assessment of cardiovascular physiology in the chick embryo

“…Due to difficulties in accessing the human fetus, animal studies are instrumental in studying how hemodynamics contribute to the patterning of the developing heart. The chick embryo ( Gallus gallus domesticus ) is a particularly well‐established model organism for developmental physiology research for over 2000 years, with roots going back to Aristotle 12,13 . The popularity of the chick embryo as a cardiovascular model arose mainly due to the visibility and accessibility of the heart and vasculature during early development, when the embryo resides on top of the yolk as it develops into a chick hatchling.…”