Comparative study of cadmium transfer in ewe and cow milks during rennet and lactic curds preparation

Cadmium transfer from whole milk to cream, rennet, or lactic curds was stud ied before and following a repeated oral cadmium administration to three la ctating ewes and one cow. Before cadmium administration, the cadmium levels in milk were around 0.4 mu g/L in ewes and less than 0.2 mu g/L in cow. Th roughout cadmium administration the mean cadmium levels in milk were 3.3 +/ - 1.4 mu g/L in ewes and 2.5 +/- 1 mu g/L in cow. During cadmium administra tion, 86% of cadmium in ewe milk was dispersed in the skimmed milk and 17% in the cream, whereas only 72% was dispersed in the cow skimmed milk and 27 % in the cow cream. Most of milk cadmium was associated with casein fractio ns. About 70% of milk cadmium was transferred to the rennet or lactic curds of ewe. The remaining cadmium present in whole milk, about 9%, was transfe rred to the rennet or lactic curd whey. In cow, the proportion of cadmium a ssociated with rennet or lactic curds, rennet curd whey, and lactic curd wh ey was, respectively, 60%, 56%, 14% and 12% of total milk cadmium. The frac tion of total cadmium transferred from milk to its milk products, whatever the species, ranged from 94% to 103%. The factor of concentration of cadmiu m from whole milk to milk products ranged from three to six. We suggest tha t the excretion of cadmium into milk is mainly achieved via the milk casein secretion. This is, to our knowledge, the first in vivo study where the ca dmium transfer from milli to its milk products after repeated cadmium oral administration to ewe and cow has been studied.