| Abstract: | Transmission of infectious agents and translocation of Cd, Cu, Pb, and Zn from anaerobically digested sludge to the tissues of farm animals grazing on pastures to which sludge was applied (2-10 metric tons per hectare) were studied on eight farms. No significant health risk associated with the possible presence in sludge of Salmonella spp., or of common animal parasites including Nematodirus spp., Strongylus spp., Strongyloides spp., Trichuris spp., Eimeria spp., Ascaris spp., and Ancylostomum spp. was noted. Caudal fold as well as cervical tuberculin testing indicated no conversions from negative to positive following exposure of cattle to sludge. Significantly higher fecal Cd concentrations were detected in samples collected from cattle soon after being placed on sludge-treated pastures compared to preexposure values in the same animals. Significant Cd and Pb accumulations were found in the kidneys of calves grazing sludge-treated pastures compared to control calves. Although older cows grazing sludge-treated pastures had significantly higher blood Pb levels, no metal accumulation was observed in other tissues. Statistically significant accumulations of Cd and Pb in the kidney of calves grazing these pastures for a relatively short period suggest that caution should be exercised to avoid prolonged grazing of cattle on pastures receiving heavy sludge applications, especially with sludges containing high concentrations of heavy metals. |
