Developmental stability in relation to population density and breed of chickens Gallus gallus.

Bilaterally symmetrical morphological characters with fluctuating asymmetry usually have small, random deviations from symmetry that reflect the ability of individuals to cope with genetic and environmental stress. A comparison of the level of fluctuating asymmetry in two fast-growing breeds (ScanBrid, Ross 208) with that of a slow-growing breed (La Belle Rouge) and wild jungle fowl from India revealed a positive relationship between growth rate and asymmetry. Fast-growing chickens kept at three densities (20, 24, and 28 chickens per square meter) revealed a positive association between fluctuating asymmetry and density. Large individuals generally had higher levels of fluctuating asymmetry than small individuals. Tonic immobility, which is often used as a measure of fearfulness, was weakly positively associated with the degree of fluctuating asymmetry (P < .05). Measures of fluctuating asymmetry may provide information on levels of stress experienced by domesticated animals.