| A corn naturally contaminated with different kind of mycotoxins but main with aflatoxin is used in this study. This study was conducted to determine the effects of graded levels of the mycotoxin-contaminated corn on the growth performance, hematology, blood biochemical parameters, anti-oxidant function and immune system of ducks. Furthermore, the cell proliferation and apoptosis, the protective effect of dietary vitamin E and organic selenium for the ducks fed the diet with contaminated corn were evaluated. This study consists of 5 experiments as followed.Experiment 1. Effect of Graded Levels of Corn Naturally Contaminated with Mycotoxins on the Performance, Hematology and Blood Biochemical Parameters in DucksSix hundred and forty 1-day-old ducks were allotted by body weight into 5 treatments with 8 replicates of 16 ducks (8 males and 8 females). Treatment 1(control) was fed diet with normal corn, and treatment 2 to 5 were fed the diets with contaminated corn substituted for normal corn by 25%,50%,75% and 100% respectively. The trial lasted for 5 weeks. The concentrations of mycotoxins in experimental diets, the weight of ducks in each replicate, and the consumption of feed were all evaluated, the number and weight of dead ducks were recorded, and the blood sample was collected at 14d and 35d respectively, to determine the hematology and biochemical parameters. As shown in the results, (1) AFB1 was the predominated mycotoxin in the experimental diet, and gradually increased with the increasing addition levels of contaminated corn, which was according to the experimental design; (2) ADFI, ADG and linearly reduced(P<0.001), F/G decreased in quadratic curve (P<0.05), and mortality linearly increased(P<0.01) with the increment of contaminated corn; (3) during 1-2 wk, the MGR of ducks was 2.05%/10 ug AFB1/kg,5GRC was 33.82 ugAFB1/kg. and during 3-5wk, the MGR was 2.15%/10ug AFB1/kg,5GRCwas 57.22 ug AFB1/kg; (4) the contaminated corn led to the decrease of RBC, increase of WBC, and the decrease of HGB, HCT, MCH during the 1-2wk with the increased significantly of activities for ALT, AST and LDH. When the ducks grew up, the concentration of RBC, GHB, HCT, MCH, MCHC and RDW in blood was reduced significantly (P<0.01). Conclusion:the corn contaminated with mycotoxins could depress the feed intake, slow down the growth, decrease the F/G, and enhance the mortality and the feed efficiency of ducks. In this experiment, there was no significant effect of contaminated corn on the growth performance of ducks when the substitution level of contaminated corn for normal corn was not more than 25%.Experiment 2. Effect of Corn Naturally Contaminated with Mycotoxins on the Performance, Anti-Oxidant Function and Immune System in DucksThree hundred and eighty-four 1-day-old ducks were allotted by body weight into 3 treatments with 8 replicates of 16 ducks (8 males and 8 females). The trial lasted for 5 weeks. The weight of ducks in each replicate and the consumption of feed were all evaluated, the number and weight of dead ducks were recorded, and the blood sample was collected when ducks were killed at 14d and 35d respectively to determine the anti-oxidative parameters in blood and liver, blood biochemical parameters, immune organ index, and specific antibody titer. The results showed that (1) ADFI, ADG and F/G was linearly reduced(P<0.01), and mortality linearly increased(P<0.01) with the increase of contaminated corn, which was similar to the results in experiment 1; (2) in the whole experiment, the serum SOD activities in 100% group was lower than that of the control group(P<0.01); with the increasing addition levels of contaminated corn, the activities of GSH-Px and CAT had the trend to decline, while the activities of MDA and the content of protein carbonyl had the trend to increase; (3) at 14 d, the activities of CAT in liver of the control group was higher than that of 50% group and 100% group (P<0.05), the activities of SOD and GHS-PX had the trend to reduce, and the activities of MDA, the content of protein carbonyl had the trend to increase. At 35d, there was no significant difference in the activities of SOD, GSH-PX, CAT, MDA, and the content of protein carbonyl (P≥0.05). Conclusion:contaminated corn resulted the oxidative stress in ducks, which caused the lesion and function changes, and consequently affected the growth performance of ducks.Experiment 3 Effect of Vitamin E and Yeast Selenium on the Performance and Immune Function in Ducks Fed Diet with Corn Naturally Contaminated with MycotoxinsFour hundred and forty-eighty 1-day-old ducks were allotted by body weight into 4 treatments with 7 replicates of 16 ducks (8 males and 8 females) in a 2x2 factoral experimental design. Normal corn and contaminated corn was used in the basal diet (VE 10 IU/kg,inorganic Se 0.2mg/kg) without or with the addition of VE+yeast selenium (YSe) (VE50IU/kg+YSe0.2mg/kg). The trial lasted for 4 weeks. The concentration of mycotoxins in experimental diets, the weight of ducks in each replication and the consumption of feed were all evaluated, while the number and weight of dead ducks were recorded, and the blood sample was collected at 14d and 28 d respectively to determine the immune organs index, humoral immunity, cellular immunity, and the content of cytokine. The results indicated (1) during the whole experiment, contaminated corn reduced the ADG and ADFI of ducks (P<0.01), but with the supplementation of VE and YSe the ADG and ADFI of ducks was increased (P<0.05); (2) contaminated corn caused varying degrees increase of liver, spleen, and Fabricius bursa index of ducks, and the decrease of the thymus index significantly, however, the supplementation group with VE and YSe could enhance the spleen index, and Fabricius bursa index. (3) there was no significant effect of either the contaminated corn or the supplementation of VE+YSe on the content of IgG, IgA and IgM (P≥0.05). However, the contaminated corn could reduce the specific antibody titer significantly, while the supplementation of VE+YSe could enhance the antibody titer. (4) the contaminated corn caused the significant decrease of peripheral blood T-lymphocyte conversion ratio and positive rate of ANAE, but opposite with the supplementation of VE+YSe. Conclusion:the supplementation of VE+YSe to diet with contaminated corn could relieve the negative effect of contaminated corn on the feed intake,growth performance and mortality, however, there was no effect of it on F/G; contaminated corn could depress the cell immunity and humoral immunity of ducks with more serious to the cell immunity., while the supplementation of VE+YSE could partly relieve the depression of immunity by the contaminated corn.Experiment 4 Effect of Corn Naturally Contaminated with Mycotoxins and Vitamin E, Yeast Selenium on the Expression of Toll-Like Receptor and Defensins Genes in Ducks1-day-old ducks were allotted by body weight into 4 treatments with 7 replicates of 16 ducks(8 males and 8 females) in a 2x2 factoral experimental design. Normal corn and contaminated corn was used in the basal diet (VE 10 IU/kg,inorganic Se 0.2mg/kg) without or with the addition of VE+yeast selenium (YSe) (VE50IU/kg+YSeO.2mg/kg). The trial lasted for 4W. The expression of TLR-1 mRNA,TLR-4 mRNA, andβ-defensins mRNA of livers and spleens of ducks at 14d were determined by fluorescence quantitative PCR. The results showed:(1)the contaminated corn increased the expression of TLR-1 mRNA of liver in ducks(P<0.01), and so did the supplementation group, but not significant (P≥0.05); contaminated corn also increased the expression of TLR-4 mRNA of liver in ducks, and so did the supplementation group(P<0.05); contaminated corn significantly increased the expression of (3-defensins, and supplement of VE+YSe could significantly up-regulate the expression of (3-defensins.(2) contaminated corn up-regulated the expression of TLR-1 mRNA, down-regulated the expression of TLR-4 mRNA of liver in ducks at 14d, without significance, and supplement of VE+YSe could down-regulateTLR-1 mRNA and TLR-4 mRNA of spleen; contaminated corn group and supplementation group both up-regulated the expression ofβ-defensins mRNA;(3)the expression of TLR-1mRNA, P-defensins mRNA of spleen was significantly higher than that of liver, the expression of TLR-4mRNA in which was higher than that of spleen. Conclusion:the innate immune system could be activated by the effect of contaminated corn on the expression of pattern recognition receptor TLR-1,TLR-4 andβ-defensins genes; supplementation of VE+SYe had accommodation for the innate immune system. Experiment 5 Effect of Corn Naturally Contaminated with Mycotoxins and Vitamin E, Yeast Selenium on the Apoptosis and Cell Proliferation of Liver and Spleen in Ducks1-day-old ducks were allotted by body weight into 4 treatments with 7 replicates of 16 ducks(8 males and 8 females) in a 2x2 factoral experimental design. Normal corn and contaminated corn was used in the basal diet (VE 10 IU/kg,inorganic Se 0.2mg/kg) without or with the addition of VE+yeast selenium (YSe) (VE50IU/kg+YSeO.2mg/kg). The trial lasted for 4wk. the apoptosis and the mitotic cycle were determined at 14d and 28d. The results showed:(1)the contaminated corn increased the apoptosis of livers and spleens, but the supplementation of VE+YSe reduced it, and there was no interaction among contaminated corn and VE+YSe; (2) contaminated corn had significant effect on cell proliferation at 14d,28d, which reduced the rate of GO/G1 cells, increased the proportion of S and G2+M period cells, and increased PI; (3) supplementation of VE+YSe could reduce GO/G1 cells of livers and spleens, and increase the proportion of S and G2+M period cells, increase PI. Conclusion:the contaminated corn either stimulated apoptosis of livers and spleens or stimulated cell proliferation, but supplementation of VE+YSe could reduce apoptosis, promote cell proliferation.ConclusionThe results indicated that diet with natural moldy corn could increase the ducks mortality, decrease the feed intake and growth performance, but improve the feed efficiency. Tissue lesion happen in livers, and the function of livers was changed with varied enzyme activities changes. Mycotoxin-contaminated corn caused the oxidative stress, and activities of anti-oxidative enzymes decreased, oxidation products (MDA, protein carbonyl) increased. Mycotoxin-contaminated corn brought about immunotoxicity to ducks with the decrease of specific antibody titer, peripheral blood T-lymphocyte conversion ratio, and positive rate of ANAE, while the expression of TLR-1,TLR-4 andβ-defensins genes of innate immune system was changed. Thus, humoral immunity and cellular immunity of ducks were depressed, and innate immunity was activated. Mycotoxin-contaminated corn also increased the apoptosis of liver and spleen, and the meanwhile stimulated the cell proliferation. Supplementation of Ve+YSe could partially eliminate the immunotoxicity of the moldy corn.
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