Uptake and Transfer of PCDD/Fs by Cattle Fed Naturally Contaminated Feedstuffs and Feed Contaminated as a Result of Sewage Sludge Application. 1. Lactating Cows

The uptake and transfer of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) was investigated in four Simmental cows with various lactation rates and body fat levels. During phase 1 a contaminant mass balance was conducted over 7 days using feed containing background levels of PCDD/Fs that were primarily of atmospheric origin. In phase 2 the same cows were fed grass silage from a field that had a history of repeated sewage sludge applications, and after 3 weeks a second mass balance was conducted over 7 days. The uptake of several of the PCDD/F congeners was up to 50 times higher during phase 2 than during phase 1. However, the transfer of these congeners to the milk was only ∼2 times lower than during phase 1. Taking into consideration the fact that the phase 2 mass balance was not conducted at steady state, it was concluded that the carry-over of PCDD/Fs entering the feed as a result of sewage sludge fertilization is not significantly different from that for feed containing background levels of PCDD/Fs of atmospheric origin.