TOXICITY, TISSUE ACCUMULATION AND RESIDUE IN EGG AND EXCRETA OF COPPER IN LAYING HENS

To study the effects of a high dietary copper dosage on the performanc e, liver function, and copper residues in the liver, egg and excreta o f the laying hen, seventy-five 28-week-old layers were selected and ra ndomly allocated to five dietary treatments with three replications of five birds each for each treatment. The feeding period was 4 weeks fo llowed by a 1 week withdrawal period. The experimental diets were supp lemented with 0, 200, 400, 600 or 800 mg kg(-1) copper. The response t o copper in the diet in terms of feed intake and egg production fitted a quadratic model (P < 0.05), with 200 mg kg(-1) giving a positive re sponse and levels of 400 mg kg(-1) and above giving a progressively ne gative response. Enzyme activities, i.e. aspartate aminotransferase (A ST), lactate dehydrogenase (LDH), and creatine kinase (CK) in the seru m were significantly (P < 0.05) increased with 600 mg of dietary coppe r inclusion. Histological examination of livers revealed damage by hig h dosages (over 600 mg) of dietary copper. Copper residues in the rive r and excreta were significantly (P < 0.05) increased as dietary coppe r increased. The copper content of egg reached a maximum at 400 mg kg( -1) dietary copper. Serum enzyme activities of AST, LDH and CK returne d to normal after the 1 week withdrawal period. Copper residues in the liver, egg and excreta also declined significantly (P < 0.05) during the withdrawal period. (C) 1997 Elsevier Science B.V.