Responses of young calves to low doses of lead.

Twenty calves, week-old male Holsteins, 42.8 kg body weight, were assigned to four treatments by oral dose 0, 1.5, 3.0, and 6.0 mg lead carbonate/kg body weight given three times weekly until calf fetal hemoglobin had been converted to 100% adult hemoglobin for 2 consecutive wk. Analyses were for the first 7 wk when data were complete. Variables included lead in blood, body weight changes, erythrocyte delta-aminolevulinic acid dehydrase activity, packed cell volume, hemoglobin, conversion of fetal to adult hemoglobin, and erythrocyte 2,3-diphosphoglyceric acid. Early changes due to lead treatment were inhibition of delta-aminolevulinic acid dehydrase at all doses and increased loss of hemoglobin at 3.0 and 6.0 mg doses. Growth rate was not impaired seriously by lead treatment. The 2,3-diphosphoglyceric acid in erythrocytes reached peak value at 3 to 4 wk of age and then decreased with age, but 2,3-diphosphoglyceric acid of the treated calves was not changed by the low lead dosing. Low lead dosing will induce early metabolic changes in the young calf prior to inhibition of growth.