Carryover of cadmium from feed in growing pigs
Growing male pigs were exposed to cadmium (Cd) at levels around 1 and 10 mg kg–1 feed for up to 12 weeks, administered as CdCl2 or Cd-cysteine (CdCys). Pigs exposed to 10 mg kg–1 showed decreased growth during the last 3 weeks. Liver and kidney concentrations of Cd continuously increased over the entire 12-week exposure, exceeding the European Union limits of 1.0 mg kg–1 (kidney) and 0.5 mg kg–1 (liver) within 3 weeks at the feed level of 10 mg kg–1. A switch to clean feed after 3 weeks for 5 or 9 weeks resulted in steadily decreased levels in kidney and liver, which could be completely attributed to organ growth. At the lower feed level, the level in kidney exceeded the limit almost twofold after 12 weeks, but not after 3 weeks. Liver levels remained below the limit. Metallothionein (MT) levels in livers showed a steady decrease in both untreated and treated animals over time. In kidney such a decrease was only observed in control animals, whereas in the highest-dosed animals the MT concentrations steadily increased. The observed carryover of Cd from feed to liver and kidney was modelled by means of a simple transfer model relating levels in feed via MT levels to accumulation of Cd. Using this model, it was shown that the exposure period of growing pigs to feed containing the European Union limit of 0.5 mg kg–1 feed should be less than 12 weeks in order to prevent Cd levels in the kidneys to exceed the European Union limit.