Relative importance of ewe milk and pasture in transferring radiocaesium to lambs during the summer grazing period

Abstract

The relative importance of milk and pasture in transferring radiocaesium (134Cs and 137Cs) to lamb's meat was studied in 13 ewes with twin lambs grazing on pastures contaminated by deposition from the Chernobyl accident. Six of the ewes were fed a caesium binder to obtain low milk radiocaesium levels and seven were used as control. Radiocaesium activity concentration was measured in meat, blood and milk every 14 d. Milk was the major source of radiocaesium for lambs younger than 6–7 wk, but from 11 wk onwards milk had only a slight and non-significant effect on radiocaesium concentration in lamb's meat. Thus, radiocaesium intake from pasture was the major factor determining radiocaesium concentration in lambs at time of slaughter. Mean aggregated transfer coefficients to meat were 23 × 10−3 m2 kg−1 and 31 × 10−3 m2 kg−1 for ewes and lambs, respectively, and mean aggregated transfer coefficient to ewes milk was 11 × 10−3 m2 l−1.