Transfer of 137Cs from grain to eggs and meat of laying hens and meat of broiler chickens, and the effect of feeding bentonite

Complete rations with 137Cs concentrations of 400 Bq/kg (deriving from grain with about 600 Bq/kg) and with 5% or 0% of the clay bentonite added were fed to eight individually caged laying hens for 4 weeks. Only minor effects of the bentonite feeding on the activity transfer was observed. The average 137Cs concentrations in egg contents were 29 and 33 Bq/kg (ca. 2Bq/egg) and in meat samples 161 and 181 Bq/kg on the rations, respectively. Transfer coefficients (day.kg-1) for 137Cs from feed to egg contents were calculated for the last 2 weeks to be 0.65 (5% bentonite) and 0.80 (0% bentonite) and to meat 3.59 and 4.04, respectively. Of total 137Cs ingested, an average of 3% was distributed in egg contents, 9% in meat of the hen carcass and 81% in excreta. Rations with similar 137Cs concentrations as for the laying hens were fed to 90 broiler chickens during selected periods of the whole 40-day growing period. As a control 15 chickens were fed with an uncontaminated ration all the time. The chickens were equally distributed into seven treatments (I-VII): Treatment I Control, Treatment II with 5% bentonite in the ration and Treatments III-VII with 0% bentonite. In the latter treatments the feeding was changed to the uncontaminated ration at different times: 0, 5, 10, 15, and 20 days before slaughter, respectively. Activity measurements were made on samples of breast meat of each carcass of the chickens when they were slaughtered on day 40. Feeding with bentonite reduced the 137Cs concentration in meat samples by 32% (105 Bq/kg in Treatment II, versus 155 Bq/kg in Treatment III). Transfer coefficients (day.kg-1) for 137Cs from feed to meat were calculated for the last 2 weeks to be 2.44 and 3.30, respectively. Changing to uncontaminated feed rapidly decreased the 137Cs levels in meat by a calculated half-life of 6 days. The bentonite feeding did not adversely influence the performance results of the chickens