Experimental lead toxicity in the ring-necked duck

Ring-necked ducks (Aythya collaris) were administered a single lead shot by gastric intubation. At weekly intervals over a 7-week period, the birds were weighed and blood samples obtained for measurement of hematocrit, free erythrocyte protoporphyrin (FEP), blood lead and delta-aminolevulinic acid dehydratase (delta-ALAD) activity. The birds were fluoroscoped weekly to ensure that the pellets had been retained. Blood lead concentrations peaked 1 week after dosing at a concentration of 7.75 micrograms/ml and then fell to control levels by Week 4. FEP concentrations in the treated ducks also peaked 1 week after dosing at levels which were roughly 1200% of control concentrations. The return of FEP concentrations to normal paralleled blood lead. ALAD activity was inhibited by approximately 85% by Week 1; however, there was a gradual but steady recovery of ALAD activity through Week 7. Four of the treated birds died within 2 to 3 weeks of lead administration. Physical signs of lead toxicity were maximal 7 to 10 days postdosing and included ataxia, loss of body weight, impaction of the upper gastrointestinal tract, and bile green diarrhea. In surviving birds, overt signs of toxicity declined with time and all birds appeared normal by Week 7.