COMPLEX STUDY OF THE PHYSIOLOGICAL-ROLE OF CADMIUM .4. EFFECTS OF PROLONGED DIETARY EXPOSURE OF BROILER-CHICKENS TO CADMIUM

A 274-day long cadmium (Cd) feeding trial was carried out with broiler cockerel chickens. The diet of the control group (Cd-0, n = 6) contai ned no added Cd, whereas to the diet of group Cd-25 and group Cd-75 (n = 10 each) 25 ppm and 75 ppm Cd was added, respectively, in the form of CdSO4. The chickens were subjected to examinations described in det ail earlier (Bokori et al., 1995b). In addition, the relative mass of five different organs (heart, liver, testis, spleen and brain), expres sed as % of the body mass, was also determined. The clinical, gross an d histopathological examinations and the assay of organs for mineral e lement content led to the following main findings. The feeding of diet s containing 25 or 75 ppm Cd for more than 9 months did not cause sign s indicative of acute Cd toxicosis or mortality in either group. The b ody mass gain of group Cd-75 chickens markedly decreased. Prolonged Cd exposure of the cockerels increased the relative mass of the liver an d heart and markedly decreased that of the testes. The change in mass was proportional to the Cd load. The Cd-fed chickens developed focal p athological fatty infiltration of the liver, histiocytic infiltration of the jejunal mucosa and focal lympho-histiocytic interstitial infilt ration and fibrosis of the kidney, which supports the view that prolon ged Cd exposure leads to the development of subacute-chronic tissue ch anges in the kidney. The Cd content of the organs increased by one to three orders of magnitude, in direct proportion to the Cd load. The Cd content of most organs was 2 to 3 times as high as the value reported for broilers exposed to a similar Cd load lasting for 68 days (Bokori et al., 1995b). This indicates that the degree of Cd accumulation is markedly influenced by the duration of the Cd exposure. The highest Cd content was demonstrated in the kidney (724 mg/kg of dry matter). The Cd exposure markedly lowered the Zn, Mo and B content of the bones an d the Ni content of the myocardium.