Effects of low level lead ingestion in sheep

Conservation efforts of captive golden takin (Budorcas taxicolor bedfordi) are potentially compromised by the elevated chemical elements exposure

Chemical elements exposure of endangered golden takins (Budorcas taxicolor bedfordi) living in the Qinling Mountains and in a captive breeding center was assessed by analyzing fecal samples. Concentrations of As, Co, Cr, Cu, Ni and Se were significantly higher in the feces of captive golden takins than the wild. There was no significant difference in the fecal concentrations of Cd, Mn, Hg, Pb or Zn for wild and captive animals. The element concentration of fecal samples collected from captive animals varied seasonally, with concentrations being lowest in spring and highest in winter and/or autumn. The food provided to captive animals varied both in the composition and the concentration of element present. Consumptions of feedstuff and additional foods such as D. sanguinalis and A. mangostanus for the captive golden takins were identified as the possible sources of chemical element exposure. The estimations of dietary intake of most elements by captive takins were below the oral reference dose, except for As and Pb, indicating that As and Pb were the key components which contributed to the potential non-carcinogenic risk for captive golden takins. In conclusion, captive golden takins were exposed to higher concentrations of chemical elements compared with the wild, which were likely due to their dietary difference. Conservation efforts of captive golden takin are potentially compromised by the elevated chemical element exposure and effort should focus on providing uncontaminated food for captive animals.

Lead toxicity to wildlife: derivation of a critical blood concentration for wildlife monitoring based on literature data

Generic risk assessments of lead (Pb) toxicity to wildlife puts soil Pb limits below the natural background. The Tissue Residue Approach (TRA) is an alternative method by which the current risk of Pb to wildlife can be assessed and avoids uncertainties about Pb exposure routes or bioavailability of environmental Pb. About 80 toxicity studies were reviewed of which 19 experimental and 6 field studies with mammals and birds were selected. Blood lead concentration (Pb-B, microg Pb/dL) was used as the index of exposure. The highest No Observed Effect Concentrations (NOECs) varied about 1600-fold among species and tests when expressed as external doses (mg Pb/kg body weight/day) whereas this range reduced to 50-fold when expressed as Pb-B. This illustrates that variation in Pb absorption from diet largely contributes to the variation in critical doses. A critical Pb-B concentration protecting mammals and birds from Pb toxicity was calculated with the HC(5) approach, i.e. the 5th percentile of species NOEC values with data of 15 different species and using growth, reproduction or hematology as endpoints. The HC(5) was significantly lower for mammals than that for birds (p<0.05), suggesting that the association between blood lead concentration and systemic toxicity was different between the two groups. The HC(5) was 18 microg/dL for mammals and was 71 microg/dL for birds. The dose-response relationship between hematological effects (hemoglobin concentration, hematocrit) and Pb-B was aggregated for different species. These relationships were highly significant and significantly different between mammals and birds. The relationships predict that the % inhibitions of hematological endpoints at the calculated HC(5) values are only 1.5% in mammals and 2% in birds, clearly within the natural variation.

Lead toxicity and metabolism from lead sulfate fed to Holstein calves

Sixteen Holstein intact male calves averaging 85 kg and 74 days of age were assigned randomly to four dietary lead treatments according to body weight. They were fed for ad libitum consumption a control diet containing no added lead or the control diet supplemented with 500, 1500, or 4500 ppm lead as lead sulfate. One calf fed 1500 ppm lead and all four calves fed 4500 ppm lead died within 6 to 10 days after initiation of treatments. Death was sudden with few or no clinical signs prior to death. Those clinical signs that did appear included muscular tremors, gnashing of teeth, bellowing, and convulsions. Four control, four 500 ppm lead, and two 1500 ppm lead-fed calves survived the 7-wk experimental period. Feed consumption, body weight changes, glutamic oxaloacetic transminase and alkaline phosphatase activity in blood plasma, and hemoglobin were not affected significantly by lead treatments. Packed cell volume in calves fed 500 and 1500 ppm added lead was reduced. Lead concentrations in blood, kidney, liver, bone, brain, and muscle were elevated in lead supplemented calves above those of controls. The highest concentrations of lead were in kidney and liver.