The influence of milk diet, grain diet, and method of dosing on lead toxicity in young calves.

Twenty 2- to 3-week-old calves were fed a milk diet or a mixture of grain and hay. After acclimatization, all calves were dosed po with lead acetate for 7 days, either in solution via a nursing bottle or in a gelatin capsule. At the end of the treatment period, 6 of 10 calves fed milk were either dead or showed multiple signs of Pb poisoning. All calves fed grain and hay appeared normal. Tissue Pb was significantly higher in calves on a milk diet (p less than 0.05) compared to tissue from calves on a grain and hay diet. No significant differences wee found when dosing methods wee compared. These data clearly show that diet but not dosing methods greatly influenced the absorption and tissue distribution of Pb in calves. delta-Aminolevulinic acid dehydratase (ALAD) activity in blood dropped to approximately 20% of pre-Pb exposure concentrations within 24 hr after the initial dose of Pb and remained at this concentration despite continued Pb administration. Blood Pb concentrations indicate that, in this model, the Pb enters the blood rapidly and retention is prolonged. The calf model warrants further studies on absorption and metabolism.