Effects of High Dietary Lead on the Metabolism of Intravenously Dosed Selenium-75 in Dairy Calves

¹ University of Georgia, Athens 30602

The metabolism of intravenously dosed ⁷⁵Se was studied in 10 Holstein bull calves fed for ad libitum access a control diet containing no added Pb or a control diet supplemented with 1000 ppm Pb as PbSO₄ for 4 wk. The Pb-supplemented calves exhibited no clinical signs often ascribed to lead toxicity. Likewise, feed intake and body weight gains were not affected adversely. The lead content of rib, kidney, liver, and brain was increased. Serum glutamic oxaloacetate transaminase activity increased in the calves fed Pb during the last 2 wk of the experiment. The kidneys of the calves supplemented with lead were 34% larger than those of controls. The total endogenous ⁷⁵Se in the feces over the 4-d collection period was not different between treatments (4.14% of dose versus 3.31% of dose). Likewise, urinary ⁷⁵Se excretion values were similar. About 97% of the ⁷⁵Se dose disappeared from the blood within 6 h after dosing four calves on both treatments. Tissue concentrations of ⁷⁵Se were reduced in kidney, spleen, pancreas, brain, and spinal cord. In summary, ingested Pb had very little effect on the endogenous excretion of ⁷⁵Se in urine and feces; therefore, the data are consistent with earlier research in which the main effect of Pb on Se occurs at the absorption site.

Key Words: selenium • lead • dairy calves

Submitted on August 7, 1989
Accepted on November 6, 1989