Growth variability in avian embryos as a source of experimental error

To reduce variability in an embryonic population to be used in experiments with electromagnetic fields, 820 Japanese quail eggs (41 experiments, 20 eggs per experiment) were incubated to analyze different possible inputs of experimental variance. Eggs came from a randombred progenitor population obtained from a poultry farm and selectively maintained. The results show that growth variability is significantly higher in some progenies, which show bimodal distributions; this is evidence of the existence of a dichotomous population with different growth velocities within these populations. This phenomenon seems to be the result of growth factors inherited from the progenitors and not of environmental factors. A genetic selection of the progenitors used in the experimental lines dealing with growth variability in birds seems necessary to reduce any possible erroneous interpretation of the experimental results.