Diet quality affects egg size and number but does not reduce maternal antibody transmission in Japanese quail Coturnix japonica

1. The ability to resist infection is an important component of survival and lifetime reproductive success. Mounting and maintaining an immunological defence is assumed to be energetically costly and nutritional resources expended on immune function may induce trade-offs with other energetically expensive functions, including reproduction. Resource limitation may even have transgenerational effects on immune function during reproduction because mothers are the primary source of humoral immunity in young vertebrates. 2. To determine whether protein restriction affects humoral immunity, either within or across generations, we fed adult Japanese quail Coturnix japonica isocaloric diets containing either the recommended protein content for reproducing adults (20%), or a low protein diet (12%). 3. Females fed the low protein diet weighed less than control females and produced fewer eggs that were smaller in size. However, dietary treatment did not affect the antibody response to a novel antigen (SRBCs) or immunoglobulin concentration (IgG = IgY) in either females or their eggs. 4. This suggests that the magnitude of the humoral immune response is either not constrained by protein availability or that birds can compensate for low dietary protein intake when fed ad libitum. Maternal protein reserves may be catabolized to support egg production and antibody formation under protein restriction such that only very severe malnutrition would affect immune function. Future work should address whether other resources mediate the trade-off between immunity and reproduction or whether other components of the immune response are impacted by resource limitation.