Effects Of Lactic Acid-Modified Zeolite On Broilers After Salmonella Pullorum Infection

This study was conducted to explore the optimal process for the preparation of lactic acid modified zeolite (LAZ) and its antibacterial effects. The effects of LAZ on performance, antioxidant capacity and immune function of broilers infected with Salmonella was determined in order to evaluate its alleviative effect on pullorum disease and the application in broiler feed. The study included three parts:In experiment1, the in vitro antibacterial effect of natural and modified zeolite on Salmonella pullorum was investigated. Different doses (0.5%,1%,2%,4%,8%, w/v) of LAZ, and1%(W/V) natural, high temperature-modified and lactic acid-modified zeolites were added in the Salmonella pullorum suspension, respectively, and cultured. Then the colony forming units were counted by plate culture. The result showed that natural and high temperature-modified zeolite had little inhibitory effect on Salmonella pullorum. Lactic acid-modified zeolite had the greatest inhibitory effect, which was enhanced by increasing the dose. The number of Salmonella decreased by99.88%when2%lactic acid-modified zeolite was added. The growth of Salmonella was inhibited completely when4%or8%lactic acid-modified zeolite was added.In experiment2, the effects of dietary LAZ supplementation on the growth performance, intestinal microflora and immune organ indexes of briolers infected with Salmonella pullorum. A total of300one-day-old AA broilers were randomly divided into five groups with6replicates of10broilers each. The treatments were as follows:1) non-infected positive control (PC) fed a basal diet;2) Salmonella pullorum-infected negative control (NC) fed the same diet;3) NC plus antibiotic (50mg chlortetracycline per kg of diet);4) NC plus2%natural zeolite (NZ);5) NC plus1%LAZ. The results showed that21-d average daily gain (ADG) of NC was significantly lower than that of PC (P<0.01), while supplementation of NZ and LAZ increased ADG by14.31%and13.84%, respectively, and their effects were similar to that of PC and antibiotics (,P>0.05). Lactobacillus counts were lower in NC group than in PC group at4,7and14d (P<0.05), while Salmonella counts were higher (P<0.05). Compared with NC, supplementation of LAZ increased lactobacillus counts (P<0.05), but decreased Salmonella counts (P<0.05) at4,7and14d. The inhibitory effect of LAZ on Salmonella was similar to antibiotic. The spleen index of NC was higher than that of PC at21d (P<0.05). Supplementation of NZ and LAZ reduced spleen index by57.8%and55.8%(P<0.01), respectively, which did not differ from that of antibiotic group.In experiment3, the effects of LAZ on the antioxidation and immunity of birds exposed to Salmonella pullorum was evaluated. The materials and methods were the same as experiment2. The results showed that NC had a numerically higher DAO activity than PC, which was reduced by antibiotic, NZ and LAZ supplementation (P<0.05). In addition, DAO activity tended to decrease with age. The serum CAT and SOD activity of NC at4d was significantly decreased (P<0.05) compared with PC. A slight decrease was also observed at21d, while the serum MDA content was significantly increased (P<0.05). Compared with NC, the4-d and21-d serum CAT activity and7-d SOD activity in LAZ group increased (P<0.05), and7-d MDA content reduced (P<0.05), while the parameters did not differ at14d. Salmonella pullorum infection increased the MDA content in jejunal mucosa at4and21d (P<0.05), reduced the7-d CAT activity in jejunal mucosa and7-d and21-d SOD activity in ileal mucosa (P<0.05). The effects of LAZ on antioxidant capacity of infected broilers were similar to those of antibiotics (P>0.05). The4-d hepatic MDA content was increased by Salmonella pullorum infection (P<0.05). Compared with NC, the7-d hepatic CAT activity increased and21-d hepatic MDA content decreased in LAZ group (P<0.05), and the effects were greater than antibiotic. The infection did not affect the serum NOS activity(P>0.05). The NOS activity in jejunal mucosa of LAZ group tended to decline at all ages compared with NC, and the effect of LAZ was similar to that of antibiotics. The IgG content in jejunal and ileal mucosa at7d and in jejunal mucosa at21d tended to be increased by Salmonella pullorum infection, which was reduced by LAZ. The same trend was also observed for jejual SIgA content at7and21d(P>0.05).