| Abstrakt: |
Cows and young steers were fed a diet containing 0 and 12% anaerobically digested Ft. Collins sewage sludge for 9 months, followed by a 4‐month withdrawal period during which no sludge was fed. Analyses of liver samples taken at intervals throughout the study showed that uptake of Cd, Cu, and Pb was linear with time. Cadmium increased from approximately 1 to about 20 ppm (dry wt) during the 9‐month sludge ingestion period. Lead and copper increased in liver tissues during the ingestion period; however, both decreased in a linear pattern after sludge was removed from the diet. There was no significant decrease of Cd levels in liver during the sludge withdrawal period. Zinc and iron levels in liver tissues were not affected by the sludge ingestion. Cadmium levels in kidney increased from approximately 5 ppm to approximately 55 ppm during the sludge ingestion period, with no significant decrease after sludge was removed from the diet. Lead and zinc concentrations in kidney increased during the sludge ingestion period, whereas Fe and Cu levels were not affected. Muscle tissues from cows and steers showed a slight, but significant, Cd increase during the sludge ingestion period. Cows showed no decrease in muscle Cd levels after the sludge withdrawal period, whereas muscle Cd concentrations of steers significantly decreased. The amount of sludge consumed by cattle during the course of this study was extreme, and would not occur under normal agricultural practices; however, even though large quantities of sludge were consumed, there were no apparent ill effects on animal health or performance. |
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