SELF-SELECTION OF LEAD SUPPLEMENTED DIETS BY CHICKS .1. EFFECTS OF LEAD ON PERFORMANCE OF CHICKS

Two experiments with various types of lead salts and different concent rations were carried out to obtain results about development, hematolo gical criteria and the retention of lead and trace elements of chicks dependening on lead intake. The one-day old chicks were kept in a cage system and fed ad lib. on a normal corn-wheat diet. In experiment 1, diets with an addition of 0; 600; 900; 1200; 2400; and 3600 ppm lead h ad been fed on chicks from day 14 to 53 of age. In experiment 2 lead a ddition of 1200; 1500; and 1800 ppm as lead-acetate, lead-carbonat or lead-chloride were used to feed chicks from day 21 to 42 of age. The e ffects of lead on the performance of the chicks were measured by feed intake, growth rate and feed conversion efficiency, the analysis of he matological criteria, and the lead and trace element contents of the e ntire carcasses. Supplementation of the diet with up to 1800 ppm lead was without significant effect on the performance of the chicks. Dosag es of 2400 and 3600 ppm lead in the diet, however, resulted in a reduc tion of live weight by 35% and 43%, respectively, compared with the co ntrol group. There were significant differences in hemoglobin content, hematokrit and mean corpuscular cell volume in comparison with the co ntrol group after a 21 days feeding period of 1200 to 1800 ppm lead. H owever, no significant differences in these hematological criteria cou ld be found after a 38 day feeding period with up to 3600 ppm lead in the diet. This showed that the chicks were able to a certain extent to counteract the lead-dependent anemia by an increase of the erythropoe se. But this reaction requires some time. The lead content in the enti re carcasses increased according with the higher lead concentrations i n the diets. Also in relation to the increase of lead content in the d iet there was a tendency of higher iron and copper contents in the car casses, but no effect on the zinc and manganese contents could be obse rved. In experiment 2, a significant higher lead content in the entire carcass was observed by using the lead-carbonate compared with lead-a cetat or lead-chlorid.