The influence of temperature on egg composition in the grey partridge Perdix perdix

Variations in egg size and composition can have important consequences for the quality of offspring. We investigated the effect of temperature, in the 5 days preceding laying, on yolk, albumen, shell and total egg mass. Moreover, we examined the influence of temperature on three important egg components, i.e. the yolk carotenoids and the albumen lysozyme and avidin. In our experimental condition food was provided ad libitum, hence we were able to remove the possible indirect effects of temperature due to a concomitant effect of temperature on food availability. Temperature on the day immediately before laying (day –1) was positively related to total egg mass and albumen mass, and negatively related to shell mass. Yolk mass was positively related to temperature in the day farthest from laying (day –5). These findings are in line with the predicted timing of the maturation of egg follicle, with yolk deposition preceding albumen and shell formation. Carotenoids and lysozyme concentration did not vary in relation to temperature, while avidin concentration was positively related to the temperature on day –1. Avidin is an albumen antibacterial substance, that could play a beneficial role during the embryonic development phases. Our results suggest that ambient temperature is an environmental factor that should be considered together with genetic and maternal effects in studies of egg quality and reproductive success.