Transfer of cadmium, lead, mercury and arsenic from feed into milk and various tissues of dairy cows: chemical and pathological data.

Abstract

In the 1st trial, lasting 3 months, 24 cows in 2 groups were given daily 15 kg roughage and 3 kg concentrates without (control) or with soluble compounds of heavy metals (including As₂O₅) added to the concentrates to give Cd, Pb, Hg and As at 2, 50, 0.2 and 3.4 (control) and 152, 200, 1.7 and 33 mg/day (treatment) resp. In the 2nd trial, lasting 2-3 lactations, 32 cows in 4 groups were kept indoors and given daily 10 kg roughage and 10-11 kg concentrates without or with soluble compounds (including As₂O₃), harbour sludge or sewage sludge. Intakes of Cd, Pb, Hg and As by control cows were the same as those in the 1st trial, but for cows in the 3 treatment groups daily intakes averaged: Cd 32, 10 and 6 mg; Pb 200, 164 and 168 mg; Hg 1.7, 3.1 and 1.2 mg; and As 33, 21 and 6.8 mg. In neither trial did increased intakes of Cd, Pb, Hg or As lead to significantly increased concn. in milk or blood, and only As given in soluble compounds was increased in muscle from slaughtered cows (4/group in trial 1 and 1-2/group in trial 2). Concentrations of Cd, Pb, Hg and As in liver and kidney were all increased by the treatments, and particularly by soluble compounds, with concn. in kidney exceeding those in liver in all but 1 case. Cd also accumulated in spleen and thymus, Pb in bone, Hg in spleen, and As in heart, thymus, spleen and brain. Results are compared with those obtained in other carry-over studies. (Abstract retrieved from CAB Abstracts by CABI’s permission)