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 studied before and following a repeated oral cadmium administration to three lactating ewes and one cow. Before cadmium administration, the cadmium levels in milk were around 0.4 microg/L in ewes and less than 0.2 microg/L in cow. Throughout cadmium administration the mean cadmium levels in milk were 3.3+/-1.4 microg/L in ewes and 2.5+/-1 microg/L in cow. During cadmium administration, 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 fractions. 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 transferred to the rennet or lactic curd whey. In cow, the proportion of cadmium associated with rennet or lactic curds, rennet curd whey, and lactic curd whey was, respectively, 60%, 56%, 14% and 12% of total milk cadmium. The fraction of total cadmium transferred from milk to its milk products, whatever the species, ranged from 94% to 103%. The factor of concentration of cadmium from whole milk to milk products ranged from three to six. We suggest that 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 cadmium transfer from milk to its milk products after repeated cadmium oral administration to ewe and cow has been studied.

Pharmacokinetics of cadmium following intravenous and oral administration to non-lactating ewes.

In a preliminary study, ewes received daily oral cadmium chloride administrations and cadmium concentration was measured in blood and tissues. A pharmacokinetic analysis of cadmium disposition was then carried out in ewes administered cadmium chloride iv and, 21 months later, orally in the same ewes. Pharmacokinetic parameters were analysed using a 3-compartment open model. The systemic availability was 0.15-0.5%, the half-life of elimination was 100-150 d, the blood clearance was 0.12-0.16 l.kg-1.d-1 and the steady-state volume of distribution was 17-35 l/kg. Following iv administration cadmium was found in tissues about 2 years later.

Indicators of lead, zinc and cadmium exposure in cattle. I. Results in a polluted area.

Dairy cattle on a farm located in the vicinity of a lead and zinc-ore processing factory were studied over 21 mo and compared with cattle on a control farm. Mean daily intakes of lead from the diet were 4.3 mg/kg body weight, with great variations; mean daily zinc intakes were 5.6 mg/kg body weight; and mean daily cadmium intakes were 0.064 mg/kg body weight. The 3 major indicators of contamination were blood lead concentrations, with mean values of 50 micrograms/100 ml of blood, zinc protoporphyrin with mean values of 165 micrograms/100 ml blood, and lead concentrations in hair which averaged 10 micrograms/g. Blood zinc concentrations and zinc concentrations were not significantly increased. One cow developed fatal post-partum paralysis. Liver, kidney and bone lead concentrations and kidney cadmium concentrations were good "post-mortem" indicators of exposure.

Indicators of lead, zinc and cadmium exposure in cattle: II. Controlled feeding and recovery.

Two pre-exposed and 2 normal heifers were fed lead (Pb), zinc (Zn), and cadmium (Cd) polluted hay (500 g/100 kg body weight) over a 17-week period. They were then examined over a 10-month period (42 or 38 weeks) to study the decay of the indicators of exposure. The elimination pattern of blood Pb and Zn protoporphyrin concentrations displayed a very slow decay. A bi-exponential equation, with the half-times of the fast component set at approximately 1 week, and the half-times of the slow component set from 3 mo to 2 years, was fitted to blood Pb levels. In man, the half-life of the slow component is still longer (2 to 15 years). This slow elimination rate represents release of Pb from skeleton, which in bovines, may accumulate up to 100 ppm Pb/dry or more. Lead concentrations in the hair were not proportionate to the areas under the curves of blood Pb levels; there was the same lack of correlation concerning skeleton and viscerae Pb levels. The withdrawal of contaminated hay from the diet resulted in a significant increase in blood copper. This is in accordance with the depressive effect of Pb and Zn on the bioavailability of this metal.