Radiostrontium transfer to sheep's milk as a result of soil ingestion

Soil ingestion as a source of radiostrontium contamination of ruminant milk products was studied by measuring the transfer coefficient to ovine milk. This is a follow-up report from a previous experiment (Assimakopoulos et al., 1993), which investigated radiocaesium transfer to sheep's milk as a result of soil ingestion. Milk samples from three lactating ewes, housed in individual metabolism cages, were used. Fifty grams per day of heavily contaminated sandy topsoil, collected in the Chernobyl area, were administered orally to the animals for a period of 1 week. The daily intake of 90Sr was 78 Bq day-1. During this contamination period, daily milk production and excreta output were measured. Excreta and milk was collected for an additional 7-day decontamination period, while they were fed on uncontaminated feed. The transfer coefficient was obtained through a best fit (minimum chi 2) of the data to predictions of a linear compartment model. The value obtained was fm = 0.041 +/- 0.016 d kg-1 for radiostrontium transport to milk. This result suggests that soil ingestion can be a major source of radiostrontium contamination in sheep and other free-grazing ruminants.