THE MAGNITUDE OF LEAD TOXICITY IN BROILER-CHICKENS

Four experiments were conducted to study the toxic effects of suppleme ntal dietary lead (Pb) on broiler chickens from hatching to 42 d of ag e. Dietary variables were 0, 0.1, 0.5 or 1.0 mg Pb/kg feed as lead sul fate in Experiment 1, and 0, 0.5 or 1 mg Pb/kg feed as lead sulfate an d lead acetate in Experiment 2. Experiments 3 and 4 were 2x4 factorial designs with 2 levels of calcium (0.65% or 1,30%) and 4 levels of Pb (0, 1, 10 or 100 mg Pb as lead sulfate/kg feed). Lead supplementation caused linear decreases in body weight gain in all experiments. In Exp eriments 1, 2 and 4, even 1 mg added Pb/kg feed caused significantly d epressed body gains. Significant negative effects of added Pb on feed conversion ratios were found at la mg Pb/kg feed. Supplemental Pb caus ed a linear decrease in delta-aminolevulinic acid dehydratase (ALAD) a ctivity. The higher level of calcium (1.30%) in the feed significantly reduced the negative effects of Pb on ALAD inhibition. Lead additions to the diet resulted in a dose-related increase of Pb in blood, kidne y, liver and tibia. Higher dietary calcium caused reduced Pb in blood and liver. Lead is toxic to chickens at much lower levels than previou sly recognized.