The development and testing of an intraruminal slow-release bolus designedto limit radiocaesium absorption by small lambs grazing contaminated pastures

The accident at the Chernobyl nuclear power plant in 1986 resulted in level s of radiocaesium in animal-derived food products above national interventi on limits in a number of countries. In upland areas of the United Kingdom ( UK) radiocaesium activity concentrations in the meat of some sheep exceeds (in 1998) the local intervention limit of 1000 Bq kg(-1) and measures are s till in place to restrict the entry of such animals into the human food cha in. The use of many established countermeasure techniques is difficult due to the nature of animal management in the affected areas. This paper descri bes a study to develop and test a bolus containing the radiocaesium binder ammonium ferric hexacyanoferrate (AFCF) suitable for administration to smal l lambs of hill-sheep breeds used in the UK. It was found that a bolus 14 m m x 50 mm in size, and containing 20% AFCF, could be safely administered to lambs of 10 kg. An increase in the AFCF content above 20% resulted in too rapid a breakdown of the bolus. Administration of three boli per lamb reduc ed the Cs-137 activity concentration in muscle by circa 50% between 3 and 8 weeks following administration of the boli. After 12 weeks the reduction i n the Cs-137 activity concentration was 30%. We conclude that the AFCF bolu s developed could be effectively used to reduce the radiocaesium activity c oncentration in lambs within hill and upland areas of the UK. (C) 1999 Else vier Science B.V. All rights reserved.