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with blood lead levels in calves, but poor correlation of ALA-D 

 with blood lead or with FEP . A study by George and Duncan (1981) 

 found levels of FEP in blood of experimental calves to be more 

 uniform than blood lead levels and that FEP levels continued to 

 rise 3 months following deletion of lead from the diet. These 

 authors suggested the FEP test could be more sensitive than blood 

 lead levels for subclinical lead exposure. Ruhr (1984) found no 

 significant correlation of FEP or ALA-D with blood lead levels in 

 normal cattle. This may have been due to the low blood lead 

 levels in the nonexposed cattle he sampled. Blumenthal et al. 

 1972 found a correlation coefficient (r) of 0.11 between the ALA-D 

 test and blood lead levels in children. These authors calculated 

 that the ALA-D test would miss 33 percent of the positive cases. 

 Furthermore, there are too few data to establish lead dose and 

 ALA-D response in cattle (Bratton and Zmudski 1984). 



Lead levels in kidney and liver tissues, both background and 

 elevated levels, are well defined for most livestock. Background 

 levels for cattle kidneys range from 0.11 ppm (calves) to 1.77 ppm 

 (Zmudski et al . 1983, Prior 1976). Similar levels for cattle 

 liver range from 0.11 ppm (Penumarthy et al. 1980) to 1.44 ppm 

 (Prior 1976). Background levels reported for horses range from 

 0.03 ppm to 1.3 ppm and 0.08 ppm to 1.4 ppm (Penumarthy et al. 

 1980) for kidney and liver tissues, respectively (Table 16). Puis 

 (1981) has reported normal lead levels for horse kidney and liver 

 at 0.5 ppm (wet weight). The tissue lead levels which are diag- 

 nostically significant for lead poisoning have been reported by 

 numerous authors. Fenstermacher et al . (1946) concluded that 10 

 ppm (dry weight) in liver tissue was a likely indication of lead 

 toxicosis. Buck et al . (1976) stated that kidney or liver levels 

 equal to or greater than 10 ppm (wet weight) were diagnostically 

 significant for ruminants. Lead levels of 3.0 to 5.0 ppm and 5.0 

 to 140 ppm (wet weight) in kidney tissue have been considered an 

 indication of lead exposure or chronic lead toxicity, respec- 

 tively, in horses (Puis 1981). Acute lead poisoning has been 

 characterized in cattle by kidney cortex levels above 25 ppm (dry 

 weight) (Todd 1962, Garner and Papworth 1967), whole kidney levels 



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