THE USE OF AN IN-VITRO TECHNIQUE TO PREDICT THE ABSORPTION OF DIETARYRADIOCESIUM BY SHEEP

The validity of an in vitro extraction technique to predict the availa bility for absorption of radiocaesium in the sheep gut has been assess ed. The technique (a 2-h extraction with caesium chloride) was found t o be valid for sources with a low availability for transfer across the gut, but inappropriate for ionic radiocaesium or radiocaesium incorpo rated internally within herbage. For such radiocaesium sources, which have a high in vitro availability, no correlation was found between in vitro extraction and true absorption measurements. A true absorption value of 0.80 is recommended for these sources, although values for in dividual sheep in the range 0.60 to 1.00 should be expected.