RELATIVE IMPORTANCE OF EWE MILK AND PASTURE IN TRANSFERRING RADIOCESIUM TO LAMBS DURING THE SUMMER GRAZING PERIOD

The relative importance of milk and pasture in transferring radiocaesi um (Cs-134 and Cs-137) to lamb's meat was studied in 13 ewes with twin lambs grazing on pastures contaminated by deposition from the Chernob yl accident. Six of the ewes were fed a caesium binder to obtain low m ilk radiocaesium levels and seven were used as control. Radiocaesium a ctivity 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, radiocaesiu m intake from pasture was the major factor determining radiocaesium co ncentration in lambs at time of slaughter. Mean aggregated transfer co efficients to meat were 23 x 10(-3) m2 kg-1 and 31 x 10(-3) m2 kg-1 fo r ewes and lambs, respectively, and mean aggregated transfer coefficie nt to ewes milk was 11 x 10(-3) m2 l-1.