Late-stage Chicken (Gallus domesticus) Embryonic Growth Patterns and Albumen Consumption

Abstract

The avian egg is a habitat in which embryos grow and develop in preparation for their next stage of life in the external environment. All nutrients, minerals, energy, and water used by the embryo during incubation are provided by female birds. Several studies have shown that there is a concomitant increase in hatchling mass with an increase in initial egg mass. We used the natural variation in the mass and composition of chicken (Gallus domesticus) eggs to examine consequences of variation in yolk and albumen mass on hatchling mass in a precocial bird. Although yolk serves as the main source of energy and nutrients, investigations have revealed that albumen also has a substantial role in embryonic development. Dzialowski et al. (2008) showed that yolk-free hatchling mass always exceeded the mass of yolk consumed suggesting that other factors (i.e. albumen) contribute noticeably to the structural growth of hatchlings. Understanding how albumen moves into and through the embryo during development may provide greater insight to its role in embryogenesis. Intrigued by the natural variation in egg size and composition, and their effect on embryonic growth, we decided to document the time-course of albumen migration through the chicken embryo and to correlate this with yolk consumption and embryo growth.