Feeding hens diets supplemented with heavy metals (chromium, nickel and lead)

The trial aims at measuring the transfer to the eggs of chromium, nickel field lead orally administered to laying hens and to evaluate the performances of the hens themselves. Ninety nine Warren laying hens, 22 weeks old, were fed for 75 d diets supplemented with three different doses corresponding to a level lower (dose 1), equal (dose 2) and higher (dose 3) than the maximum tolerable level of the three metals. The doses were 500, 1,000, 2,000 ppm for Cr as CrCl3, 100, 300 and 500 ppm for Ni as NiSO4 and 20, 30 and 100 ppm for Pb as PbO. Chromium residues in albumen ranged from 76 to 153 ppb, in yolk from 132 to 713 and in shell from 17 to 145 ppb. Nickel concentrations were particularly unsteady: from 71 to 964, 196 to 2,259 and 115 to 345 ppb respectively for albumen, yolk and shell. The Pb concentrations ranged from 315 to 1,257, 397 to 1,191 and 69 to 293 ppb respectively for albumen, yolk and shell. The eggs of the treated groups had a higher content of the metal tested even if not always proportional to the dose received by the hen. The levels of Ni and rb in the eggs increased when the dietary treatment was prolonged from 30 to 75 d. The ratio of lead transferred to the edible part of the egg (0.1%) was higher compared with nickel (.0334%) and chromium (0.0026%). Egg production and egg quality (weight of whole egg and of whites) were negatively and significantly affected by heavy metals.