Quantitative Morphometric, Physiological, and Metabolic Characteristics of Chickens and Mallards for Physiologically Based Kinetic Model Development

Physiologically based kinetic (PBK) models are a promising tool for xenobiotic environmental risk assessment that could reduce animal testing by predicting in vivo exposure. PBK models for birds could further our understanding of species-specific sensitivities to xenobiotics, but would require species-specific parameterization. To this end, we summarize multiple major morphometric and physiological characteristics in chickens, particularly laying hens (Gallus gallus) and mallards (Anas platyrhynchos) in a meta-analysis of published data. Where such data did not exist, data are substituted from domesticated ducks (Anas platyrhynchos) and, in their absence, from chickens. The distribution of water between intracellular, extracellular, and plasma is similar in laying hens and mallards. Similarly, the lengths of the components of the small intestine (duodenum, jejunum, and ileum) are similar in chickens and mallards. Moreover, not only are the gastrointestinal absorptive areas similar in mallard and chickens but also they are similar to those in mammals when expressed on a log basis and compared to log body weight. In contrast, the following are much lower in laying hens than mallards: cardiac output (CO), hematocrit (Hct), and blood hemoglobin. There are shifts in ovary weight (increased), oviduct weight (increased), and plasma/serum concentrations of vitellogenin and triglyceride between laying hens and sexually immature females. In contrast, reproductive state does not affect the relative weights of the liver, kidneys, spleen, and gizzard.

Automated summary

Physiologically based kinetic (PBK) models can help reduce animal testing by predicting in vivo exposure, and understanding species-specific sensitivities to xenobiotics is crucial for environmental risk assessment. In this study, we conducted a meta-analysis of published data to summarize the morphometric and physiological characteristics of chickens and mallards. The distribution of water and the lengths of small intestine components are similar in both species. Furthermore, the gastrointestinal absorptive areas are comparable to those in mammals. However, there are significant differences in cardiac output, hematocrit, and blood hemoglobin levels between laying hens and mallards. Additionally, reproductive state affects ovary and oviduct weights as well as plasma/serum concentrations of vitellogenin and triglyceride.