Relationship of plasma estradiol and progesterone levels to egg productivity in domestic chicken hens

Female chickens from eight different genetic stocks, ranging from 13 to 21 months of age, and exhibiting various levels of egg production were studied. Plasma samples were collected between 1700 and 2200 hr to determine basal circulating levels of progesterone (P4) and 17 beta-estradiol (E2) by radioimmunoassay. Linear regression analysis was used to describe the relation between mean hormone levels (E2, P4, and E2/P4) and mean egg production from these groups, and correlation coefficients were used to evaluate the general usefulness of these hormone parameters for estimating egg production within a group or flock of hens. Of the three hormone parameters evaluated, basal circulating E2/P4 was found to be the best estimator of egg productivity.