Study Of The Effects Of Zinc-bearing Attapulgite On Anti-bacterial Capacity And Immunity Regulation Of Broilers And Its Relative Mechanism

The purpose of this work was to explore the optimal operation condition of loading zinc ion in attapulgite, to test antibacterial characteristic of zinc-bearing attapulgite, and to study the effects of zinc-bearing attapulgite on growth performance and immune regulation of broilers. The results would be some information for the reasonable application of attapulgite and the exploitation of new type feed additives.This study included three parts and their results were presented as follows:The zinc-bearing attapulgite was prepared by the ion exchange method in the first experiment, and the effects of ion concentration, pH value, temperature of solution and action time on the exchange quantity were studied. The structure was characterized by X-ray diffraction (XRD), the zinc ion content was measured by atomic absorption spectrophotometer, and the antibacterial function of zinc-bearing attapulgite on Escherichia coli., Staphylococus and intestinal microflora of broiler jejunum were examined also. The results showed that the concentration of exchange solution of 1mol/L, the pH value at 4, the exchange time of 3 hours and the temperature at 60℃were the optimum operation condition; the zinc ion content of zinc-bearing attapulgite was 2.55%; the zinc-bearing attapulgite restrained the growth of Escherichia coli. significantly in the germiculture experiment; the zinc-bearing attapulgite decreased the count of Escherichia coli and increased the count of Lactobacillus in broiler jejunum.The second experiment was designed to study the effects of zinc-bearing attapulgite on performance, immunity of borilers and its mechanisms. Six hundred one-day-old AA broiler chicks were randomly allocated to five treatments, of 12 pens for 10 replicates. The birds of group 1 were fed the basic diet of addition ZnSO₄, group 2 were fed the basic diet of ZnSO₄ + antibiotic, group 3, group4, group5 were fed the basic diet supplemented with zinc-bearing attapulgite at the level of 0.16%,0.32%,0.48% respectively. The contents of zinc in 5 treatment diets were 80 mg/kg, 80 mg/kg, 40 mg/kg, 80 mg/kg, 120 mg/kg respectively. The growth performance, cell immunity, blood biochemical index were measured in this experiment, and from the aspects of small intestine morphology, the main bacterial quantity in jejunum to explain the mechanism. The results showed: 1.Zinc-bearing attapulte supplemented in diet improved the performance in starter phase, the difference of 0.32% and 0.48% group were significance (P<0.05), but had no signicicant effects on feed convert ratio ( P>0.05 ) ; zinc-bearing attapulte supplemented in diet improved the growth performance significantly in growth phase (P<0.05), but had no signicicant effects on feed convert ratio (P>0.05) . 2. Supplementary attapulgite of different level in diet promoted the weight of immune organ both in starter and growth phase, the bursa weight in starter phase of the 0.48% group was significantly improved (P<0.05 ) , the spleen weight in growh phase of the 0.32% group was significantly improved (P<0.05); attapulgite supplement in diet had the trend of improving the cell immunity in growth phase, and the lymphocyte quantity in blood was improved significantly by the supplementary of 0.48% attapulgite(P<0.05); attapulgite supplemented in diet improved the activity of AKP in blood both in starter and growth phase, and the difference was significant in the 0.48% group (P<0.05); there were no significant effects on the activity of lysozyme in blood in starter phase (P>0.05) , the activity of lysozyme in blood in growth phase increased significantly by supplementary of 0.48% zinc-bearing attapulgite (P<0.05) . 3. The V/C value in duodenum in the starter phase increased with the increasing levels of supplementary zinc-bearing attapulgite; the V/C value in duodenum in the growth phase significantly increased both in the 0.32% and 0.48% group (P<0.05) ,the villus height and V/C value in jejunum in the growth phase great significantly increased in the 0.48% group (P<0.01) . 4. Supplementary attapulgite in diet had the trend of decreasing the quantity of Escherichia coli in jejunum in the growth phase, the quantity of lactobacillus in jejunum significantly increased both in the group of 0.16% and 0.48%.The effect of zinc-bearing attapulgite on antioxidant capacity and metallothionein content in liver of broilers were explored in the third part. The experiment design was as same as that in the second part. The activity of SOD, GSH-Px, CAT and the content of MDA, MT in the liver were measured at the age of 21 and 42 days. The results showed: 1. In the starter phase, three were no consistent effect of zinc-bearing attapulgite on the activity of SOD, the activity of CAT, the content of MT increased and the content of MDA decreased with the increased level of supplementary zinc-bearing attapulgite, and the effects on the activity of CAT and the content of MDA were significant both in the 0.32% and 0.48% group (P<0.05) . 2.There were no significant effects of zinc-bearing attapulgite on the activity of SOD,GSH-Px and the content of MDA in the liver at the growth phase, had the trend of improving the CAT activity and MT content, the content of liver MT in growth phase was improved significantly in the 0.48% group (P<0.05) . In summary, three works indicated that zinc-bearing attapulgite had the character of antibacterial in vitro, improved the growth performance, antioxidant ability of liver and regulated the immunity of broilers. The mechanism of zinc-bearing attapulgite in improving the growth performance was explained by meliorating the morphology of small intestine, restraining the propagate of harmful bacterial and promoting the propagate of helpful bacterial to enhance the immunity, and giving impact on the content of MT to influence the antioxidant capacity.