The importance of the gut and its contents in prey as a source of cadmium to predators.

Many mammalian and avian predators consume the whole carcass of their small mammal prey. Thus, the contaminant load of the gut and its contents may be of toxicological significance, but pollutant loads in the gut of prey species are often not measured and their role in food-chain transfer of contaminants is largely unquantified. We investigated the importance of the gut and its contents in prey as a source of cadmium (Cd) to predators by measuring the Cd concentrations in the guts (including contents), in various body tissues, and in the intact bodies of wood mice (Apodemus sylvaticus). The mice had been fed for up to 365 d on either control, a medium-Cd (MCd) diet, or a high-Cd (HCd) diet that had nominal Cd concentrations of 0, 8, and 40 g/g wet weight, respectively. In wood mice fed contaminated diets, Cd was progressively bioaccumulated in all the body tissues that were analyzed. The gut (and contents) and the liver and kidneys (the critical organs) contained most of the accumulated Cd and were the only significant contributors to the total body burden (TBB). The contribution of the gut (and contents) to the TBB was greater in mice fed MCd diet than in those given HCd feed but declined with age (equivalent to exposure duration) in both groups as Cd in the critical organs increasingly became the most important source of TBB Cd. However, the gut and its contents contributed between 50 and 100% of the Cd TBB in mice fed for up to six months on MCd diet; this was the diet that most closely mimicked the estimated average Cd intake of wood mice on contaminated sites. The results of this study highlight the importance of including measures of Cd load in the gut when modeling food-chain transfer from small mammals to their predators.