0141755 



has been shown to range from 0.3 percent to 5 percent in various 

 animals (Doyle et al. 1974, Moore et al. 1973, Miller et al. 1967) 

 and is similar to the 2.7 percent absorption found for humans 

 (Newton et al. 1984). Data suggest diets deficient in protein and 

 calcium may increase cadmium absorption or retention (Larsson and 

 Piscator 1971, Suzuki et al. 1969). Elevated concentrations of 

 zinc, copper, iron, selenium or ascorbic acid tend to reduce the 

 deleterious effects of this element (Pond and Walker 1972, Hill et 

 al. 1963, Gunn et al . 1968). Cadmium retained by the gastrointes- 

 tinal tract appears to represent the fraction most rapidly cleared 

 from the body, usually within 4 to 12 days for cows and goats (NRC 

 1980). Lesser amounts of absorbed cadmium are excreted via bile, 

 intestinal tract wall and urine. Very small amounts (.002 ppm) of 

 cadmium have been detected in milk from Holstein cows which 

 suggests milk is not an important factor in the excretion of 

 cadmium from the body (Miller et al. 1967). Excretion of cadmium 

 via the urine increases markedly following renal damage but prior 

 to tissue damage, urine is an erratic indicator of cadmium 

 exposure . 



The most common signs of cadmium poisoning in livestock are 

 reduced growth rates in young animals, anemia, infertility, 

 abortions and deformed young. Sheep fed cadmium have lost the 

 crimp in their wool, a characteristic of copper deficiency (NRC 

 1980). 



The physiological action of cadmium within the body is 

 intimately associated with zinc metabolism. Cadmium apparently 

 leaves the blood rapidly following absorption and accumulates to 

 some extent in most organs in the body. Both zinc and cadmium are 

 known to induce the synthesis of the protein thionein to which the 

 metals become bound (Cousins 1979). Cadmium metallothionein 

 eventually accumulates in the liver and kidneys; kidneys have the 

 highest concentration. The degradation of metallothionein has 

 been shown to follow the order thionein < zinc metallothionein < 

 cadmium metallothionein. When cadmium metallothionein is de- 

 graded, the released cadmium ions are quickly incorporated into 

 nascent chains of thionein and retained within the bodv (Cousins 



15* 



