| AbstracttThe experiment was conducted with the object of investigating pathological changes produced by Zn deficiency and toxicity. 150 one-day-old Tianfu ducklings were randomly divided into 3 groups,and fed on diets as follow:1. Zn deficiency (22.9mgZn/kg diet),2. control (lOOmgZn/kg diet),3. Zn toxicity (1300mg/kg diet) for seven weeks(ZD) or four weeks(ZT). In Zn deficient group,morbidity was 80%. Effected birds showed hypogenesis of feather and break of web. Histopathologically,the tongue epithelium showed little ulcers,the web skin was hyperkeratosis companied with infiltration of heterophils. Lymphocytes of thymus,bursa of Fabricius and spleen were significantly depleted,degenerated and necrotic. Concentrated uncleolus,mitochondria swelling and dilatated rough endoplasmic reticulum were ultrastructurally observed in the lymphocytes and reticulocytes of immune organs. Haematologically,the red cell count,hemoglobin,serum gross protein,albumin,globulin ,serum zinc contents and serum AKP activities reduced (PO.05 or P<0.01) compared with the control group. In Zn toxic group,the morbidity and mortality were 100% and 90% respectively. The result suggested that high dietary Zinc suppressed weight gain and induced anorexia,anaemia and paralysis.At necropsy,muscles in the leg were white or grayish-white. The white stain appeared in the smooth muscle of gizzard. The digestive tract was full of the black-brown substance. Histopathologically,skeleton muscle was degenerated and necrotic.The cardiac muscle and smooth muscle of the gizzard showed local necrosis. Congestion and degeneration in the liver were discovered. The histologic and ultrastractural changes of thymus ,bursa of Fabricius and spleen were similar to Zinc deficient ducks. Haematologically,the red cell count,hemoglobin,serum gross protein and globulin contents were much lower and the serum glulamic-pyruvic transaminase activities,serum Zn contents were much higher(P<0.01) in Zn toxic group than in control group(P<0.05).
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