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

      , , , , ,
      Chemosphere
      Elsevier BV

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          Abstract

          High level of PCDD+PCDF contamination in bulk milk (9.7 pg WHO-TE g(-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 10.4 ng WHO-TE kg(-1) dry matter. In-farm produced hay and silage showed levels not exceeding 0.2 ng WHO-TE kg(-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 3.0 pg WHO-TE g(-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 5 pg WHO-TE g(-1) fat, compared to the 10 pg WHO-TE g(-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.

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          Author and article information

          Journal
          Chemosphere
          Chemosphere
          Elsevier BV
          00456535
          August 2008
          August 2008
          : 73
          : 1
          : S216-S219
          Article
          10.1016/j.chemosphere.2007.11.071
          18462776
          77ac0bb6-4974-4728-86d8-cee434ff650e
          © 2008

          https://www.elsevier.com/tdm/userlicense/1.0/

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