| Effects of various dose of nano-zinc oxide on the immunological regulation function, expression of some cytokine and MT in vivo and the correlated mechanisms in Arbor Acre broiler(AA) were studied, and Screening appropriate dosage for nano-zinc oxide. AA broiler was taken as the test animal and used single-factor experimental design in the study, 125 healthy AA broilers at 1 day of age were randomly divided into 5 groups. The control group fed by basal diet which contained 50 mg/kg of nano-zinc oxide and the rest of the test groups were fed with 100 mg / kg, 200mg/kg, 400mg/kg and 800 mg / kg diet respectively from low to high nano-zinc oxide dose for a 28-day trial. The results showed as follows:1. Compared to the control group, it was found that groups of 100mg/kg and 200 mg/kg nano-zinc oxide could significantly increase immune organs and the weight index of 14-day-old broiler(P <0.05), the thymus index and ANAE+ lymphocytes percentage in peripheral blood of the control group were the highest at 21 and 28 days, while the spleen index of 200 mg/kg dose group was the best (P <0.05), 100 mg/kg dose of nano-zinc oxide was conducive to the development of bursa Fabricii and can effectively enhanced the 21-day-old broiler serum hemolysin titer. In these three stages, the dose groups fed with 400 and 800 mg/kg nano-zinc oxide led to an apparent inhibitory action on immune organ growth and development, cell-mediated immunity and humoral immune function.2. Appropriate amount of nano-zinc oxide contribute to increase the RBC-C3bRR rate , RBC-C3bRR rates began to decrease straight when the dose as high as 400 mg/kg, and RBC-ICR rate increased significantly at the same time, but the red blood cell adhesion immune function of the high-dose group was affected significantly.3. Added 100 mg/kg nano-zinc oxide in the diet was conducive to spleen IL-6 gene expression of AA broiler, and IL-2 gene expression with regular doses of zinc group (50 mg/kg) was the best. In high doses of the role of nano-zinc oxide,IL-2 and IL-6 gene expression not only failed to promote, but show significantly inhibition. 4. In a certain dose range, broiler serum zinc and MT both had a clear dose-response relationship with the level of nano-zinc oxide in the diet, compared with the control group, these two indicators was significantly improved (P <0.01), and could cause protection from the toxic accumulation resulted by zinc to great degree .To sum up, nano-zinc oxide had a two-way immune regulatory function, appropriate amount of nano-zinc oxide can help to strengthen the body's immune cells and humoral immune function and red blood cell immune function, and promote cytokine and MT expression. The body showed sub-clinical toxicity with immune function-specific and non-specific immune functions were subject to inhibit while the excessive use of nano-zinc oxide for long time. In order to alleviate the toxic effects of zinc, the body is given maximum protection to resist the excessive accumulation toxicity of Zinc via regulating the expression of MT. |
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