GRINDSTAFF, J.L.: Dietary protein restriction does not suppress humoral immune function or maternal antibody transfer in Japanese quail (Coturnix coturnix japonica)
The ability to resist infection is an important component of survival and lifetime reproductive success. Many current theories in ecological immunology assume that mounting and maintaining an immunological defense is energetically costly and nutritional resources expended on immune function may necessarily be traded-off with other functions including reproduction. Females passively deposit antibodies in egg yolk during egg formation that provide the sole form of humoral immune defense for newly hatched young. To determine the influence of dietary protein on reproduction and humoral immunity in adults and passive antibody transfer to eggs, I maintained adult Japanese quail (Coturnix coturnix japonica) on isocaloric diets containing either the recommended protein content for reproducing adults (20%) or a low protein diet (12%). Birds fed the low protein diet weighed less than control birds, and females produced fewer eggs that were smaller in size. Although the weight of females was positively correlated with antibody response to a novel antigen, adult antibody response did not differ between dietary treatments. There was also no difference in antibody titer between eggs laid by low protein and control females. These results provide the first evidence that in Japanese quail, humoral immune function is not suppressed in order to divert limited protein resources to reproductive function.