Physiological parameters that affect the transfer of radiocaesium to ruminants.

Recently there has been a renewed interest in biological scaling relationships between parameters, such as those between, for example, body mass, dry matter intake and biological half-times of radionuclides that are useful in predicting the transfer of radiocaesium to different animal species, particularly to wild animals. However, there is still a considerable unexplained variability in transfer coefficient estimates between individuals of the same species. This paper discusses the physiological parameters that affect the transfer of radiocaesium to ruminants, and it shows how a better understanding of these parameters may help to reduce the within-species variability in radiocaesium transfer coefficients. In light of the improved understanding during the past 10-15 years of the importance of source-dependent bioavailability on absorption of radiocaesium from the gastrointestinal tract, it is concluded that further studies are required on the effects of feed digestibility and physiological factors on absorption and endogenous faecal excretion of radiocaesium to better understand the variability in transfer coefficients.