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PCDD and PCDF depletion in milk from dairy cows according to the herd metabolic scenario

PCDD and PCDF depletion in milk from dairy cows according to the herd metabolic scenario,10.1016/j.chemosphere.2007.11.071,Chemosphere,Gianfranco Bram

PCDD and PCDF depletion in milk from dairy cows according to the herd metabolic scenario   (Citations: 4)
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High level of PCDD+PCDF contamination in bulk milk (9.7pgWHO-TEg−1 fat) from 1604 Holstein Fresian lactacting cows was observed just four weeks after the beginning of their exposure to a feed supplement contaminated at 10.4ngWHO-TEkg−1 dry matter. In-farm produced hay and silage showed levels not exceeding 0.2ngWHO-TEkg−1 dry matter. After the supplement withdrawal, it was possible to monitor the depletion phase for a following 75-day period in milk, until the levels dropped well below 3.0pgWHO-TEg−1 fat, the EU regulatory Maximum Residue Level for PCDD+PCDF. During this phase, the half-life was calculated as 17±3 days, on WHO-TEQ basis. The full availability of farm data on both cow nutrition and milk production allowed the calculation of the carry-over rate (COR) (PCDD+PCDF milk excretion vs. feed), which was 46% at the end of the exposure. This COR value is justified from the main TE contribution of Penta-CDD and -CDF congeners (63%), and the half-life is among the shortest of all those described in the literature both for experimental and naturally-exposed dairy cows. A fugacity-based model predicts a bulk milk contamination of 5pgWHO-TEg−1 fat, compared to the 10pgWHO-TEg−1 fat level observed. Such findings are discussed in light of the lactation and metabolic status of the herd for which the transition period, characterised by a negative metabolic energy balance and a consequent adipose tissue mobilization, could play a relevant role.
Journal: Chemosphere , vol. 73, no. 1, pp. S216-S219, 2008
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