The relationship of serum calcium to shell weight and other criteria in hens laying a low or high incidence of shell-less eggs.

Experiments were conducted to determine the relationship of serum calcium to shell weight and other criteria. Blood samples for calcium analysis were taken at oviposition in Experiments 1 and 2 from hens fed a 3.5% calcium diet. In Experiment 3, blood was taken at various intervals from hens laying a high or low incidence of shell-less eggs. These hens were fed a control diet or various calcium-deficient diets throughout a 45-day period. No relationship was found between serum calcium and shell weight, or egg weight. Hens laying a high incidence of shell-less eggs showed no decrease in serum calcium or egg production when fed a .58, .25, or .07% calcium diet. However, these criteria were reduced in hens laying a low incidence of shell-less eggs. It was concluded that the normal variation in serum calcium is not related to the hen's ability to produce eggshell. The mechanism of action responsible for cessation of lay when control hens were fed a calcium-deficient diet appeared not to function as it does in hens laying a high incidence of shell-less eggs.