The transfer of different forms of 35S to goat milk

Sulphur-35 is released during the routine operation of UK gas-cooled reactors. An experiment to determine the rates of transfer of different forms of (35)S to goat milk is described. Lactating goats received (35)S orally as single administrations of sulphate, L-methionine, or grass contaminated either through root uptake of (35)S as sulphate or through aerial deposition of (35)S as carbonyl sulphide onto the grass. Transfer was higher for (35)S administered as methionine compared with (35)S administered as sulphate. Changes in activity concentrations in milk for all sources of (35)S demonstrated two components of loss. The first component had a half-life of circa 1 d for all sources, the second was longer in goats administered carbonyl sulphide (44 d) than in all of the other treatments (circa 10 d). The rate of transfer of (35)S to milk of a further group of goats receiving (35)S-sulphate daily appeared to reach equilibrium within 30 d. Extrapolation of transfer parameters derived to other dairy ruminants is discussed.