Effect Of Dietary High Molybdenum On Immune Organs And Immune Function In Broilers

300 one-day-old Avian broilers were randomly divided into four groups,and fed on diets as follows:control diet (Mo 13mg/kg) and high molybdenum diets(Mo 500 mg/kg, high molybdenum groupⅠ; Mo 1000 mg/kg, high molybdenum groupⅡ; Mo 1500 mg/kg, high molybdenum group III) for 6 weeks. The experiment was conducted with the objective of examining the impact of high molybdenum on immune function in broilers by methods of experimental pathology and flow cytometry (FCM). Results were as follows:1. Spleen No obvious changes were observed in high molybdenum group I. Lymphocytes were histopathologically decreased in high Mo groups II and III. Ultrastructurally, the frequency of lymphocyte apoptosis was higher in high Mo groups II and III than in control group. The mitochondria were swelled, the endoplasmic reticulum and the Golgi apparatus were dilated. The statistical analyses by FCM indicated that the G0/G1 phase was increased and the G2+M phase, S phase and the PI (Proliferating index) were decreased (P<0.01) of spleen in high molybdenum groups II and III. Meanwhile, the percentage of cellular apoptosis was higher in high molybdenum groups II and III than in control group. Also, the TUNEL staining was consistent with the result of FCM. The splenic superoxide dismutase (SOD) and glutathion peroxidase (GSH-Px) activities were decreased (p<0.01), and malondialdehyde (MDA) contents were increased (p<0.01) in high Mo group II and high Mo group III compared with those of the control group.2. Thymus Decreased lymphocytes, enlarged Hassall's corpuscles and increased myoid cells were observed in high molybdenum groupsⅠ,ⅡandⅢin comparison with those of control group histopathologically. The mitochondria were swelled and the frequency of lymphocyte apoptosis was higher in high molybdenum groupsⅠ,ⅡandⅢthan in control group ultrastructurally. The statistical analyses by FCM indicated that the G0/G1 phase of thymocyte was increased and the G2+M phase, S phase of thymocyte and the PI were decreased (P<0.05 or P＜0.01) in high molybdenum groupsⅠ,ⅡandⅢ. Meanwhile, the percentage of cellular apoptosis was higher in high molybdenum groupsⅠ,ⅡandⅢthan in control group. Also, the TUNEL staining was consistent with the result of FCM.3. Bursa of Fabricius Lymphocytes were histopathologically decreased and reticulocytes were increased in number in high molybdenum group II and III. Ultrastructurally, the frequency of lymphocyte apoptosis was higher in high molybdenum groups II and III than in control group. The mitochondria were swelled and mitochondria cristas were broken, or the density of mitochondrial matrix was increased. The statistical analyses by FCM indicated that the G0/G1 phase was increased and the G2+M phase, S phase and the PI were decreased (P<0.01) of bursa of Fabricius in high molybdenum groups II and III at 28 and 42 days of age. Meanwhile, the percentage of cellular apoptosis was higher in high molybdenum groups II and III than in control group. Also, the TUNEL staining was consistent with the result of FCM.4. The activities of SOD and GSH-Px in serum were decreased (p<0.01), and malondialdehyde (MDA) contents were increased (p<0.01) in high Mo group II and high Mo group III compared with those of the control group. The percentages of CD3+, CD3+CD4+and CD3+CD8+ were decreased in high Mo group I, II and III in varying degrees. Also, the serum interleukin-2 (IL-2) contents were decreased in high molybdenum groups II and III(P<0.01). The detection by immunoturhidimetry indicated that the serum IgG and IgM contents were much lower in high molybdenum group I, II and III than in control group (P<0.01), and the serum IgA contents were not different in comparison with those of control group.It was concluded that dietary molybdenum in excess of 500 mg/kg inhibited the development of thymus. However, dietary molybdenum in 1000 mg/kg and 1500 mg/kg could depress antioxidative function of broilers and inhibit the development of the spleen and Bursa of Fabricius. Pathological changes in the immune organs and impaired the function of cellular immunity and humoral immunity in broilers.