RESTRICTION OF CADMIUM TRANSFER TO EGGS FROM LAYING HENS EXPOSED TO CADMIUM

The transfer of Cd to eggs of white Leghorn laying hens has been shown to be restricted. After Cd was injected ip into laying hens, the Cd c oncentrations in the blood, livers, ovaries, and eggs were measured. A lthough the Cd concentrations in the maternal blood and livers increas ed remarkably at certain levels of administrations, the Cd concentrati on in the yolks of eggs was not significantly increased, and was less than 0.04 mu g/g wet weight. After egg production stopped in the highe st injected group (7.5 mg Cd/kg), Cd in the yolks of eggs had an accum ulated range of 0.02-0.03 mu g/g wet weight. This was despite the high Cd accumulation in the liver. Furthermore, the Cd concentration in th e follicle walls of the ovary increased and was 13- to 52-fold higher than in the follicle yolks. An additional experiment was conducted in order to estimate whether hatching success is affected by the Cd in th e laid eggs of Cd-injected laying hens. The ratio of hatching success in the 0.3 or 1.2 mu g Cd/egg-injected groups was similar to that in t he saline-injected group, indicating that a small amount of Cd in the eggs might exert no marked influence on the hatching success. In concl usion, Cd transfer from laying hen to eggs was restricted after the ma ternal bird was exposed to Cd. Furthermore, Cd accumulates in the foll icle walls of ovary. These results suggest that the follicle walls mig ht play a role in protecting the follicle yolks against Cd toxicity.