Several hens were fed by adding ammonium chloroiridate into their forage. After two weeks

the Ir concentration in three fractions (eggshell

albumen

egg yolk) of their eggs were measured by INAA. Ir was found in all of the three parts. However

the highest concentration of Ir was found in the egg yolk fraction

which was about 10 times higher than that in the eggshell and albumen. Moreover

the longer the Ir-containing feedstuff was used

the higher the Ir concentration in the egg fractions was. After 7-8 days feeding

it kept stable. On the other hand

as soon as adding the Ir-containing additives were stopped

the Ir concentration in the egg fractions fell down quickly. The experimental results indicated that the ratio from the feedstuff to the eggshell via gastrointestinal pathway to be about 0.07 percent. The new result might be beneficial to explain the iridium-enriched dinosaur eggshell fossils and to interpret the origin of the mass extinct event of dinosaur occurred at the end of Cretaceous.