Effects Of Single-Atom Additives On Growth Performance And Disease Resistance Of Sanhuang Chicken

In this paper,the in vitro bacteriostatic test of single-atom additive was carried out,its stability and safety were investigated,and the effects of single-atom additive on growth performance,immune function and intestinal microflora of Sanhuang chicken were observed.the addition amount of single-atom additive in Sanhuang chicken diet was screened.The protective effect of single-atom additive on Salmonella typhimurium in Sanhuang chicken was carried out in order to provide theoretical basis for the application of single-atom additive in livestock and poultry breeding.The main research contents and results are as follows:1.In vitro inhibition effect of single-atom additives on pathogenic bacteria,stability and safety testsThe single-atom additives were formulated into different concentrations of suspensions,and their in vitro inhibition effects were investigated through in vitro co-culture.The results showed that the single-atom additive had a good inhibitory effect on Salmonella Typhimurium,Escherichia coli,and Staphylococcus aureus,with a minimum inhibitory concentration of 3.125 mg/mL and a minimum bactericidal concentration of 50 mg/mL.Temperature and pH did not have a significant effect on the inhibitory action of the single-atom additive.The results of the acute oral toxicity test and the acute irritation test showed that the single-atom additive had no toxic side effects or irritation to the test animals.2.Effects of single-atom additives on the production performance and immune function of Sanhuang chickensOne hundred and fifty 1-day-old Sanhuang chickens were randomly divided into three dose test groups(LSA,MSA,HSA),a control group(DC),and a blank group(NC).Different doses of single-atom additives or trace element premixes were added to the basal feed for the test and control groups,respectively,while the blank group was given the basal feed.The test period was 42 days,including two stages:the first(1-21 days of age)and the second(22-42 days of age).The results showed that the single-atom additives significantly increased the average daily gain(P<0.05);In the early of the experiment,The spleen index of the MSA group was significantly higher than that of the DC group(P<0.05);the serum IgA,IgM,and IgG contents of the HSA group were significantly higher than those in the NC group(P<0.05);serum avian influenza(AI)antibody titers were significantly higher in the LSA group than in the NC group(P<0.05),and serum Newcastle disease(ND)antibody titers were significantly higher in the DC group than in the NC group(P<0.05);jejunal and duodenal villi heights(VH)were significantly higher in the MSA group than in the NC group(P<0.05),and jejunal and duodenal crypt depths(CD)in the HSA and LSA groups were significantly lower than those in the NC group(P<0.05).At the end of the experiment,the serum IgM content of the HSA group was significantly higher than that of the other test groups(P<0.05),the jejunal and duodenal VH of the HSA group was significantly higher than that of the NC group(P<0.05),and the CD of the jejunum of the HSA and MSA groups was significantly lower than that of all other test groups(P<0.05).3.Experimental study of single-atom additives on the prevention of Salmonella typhimurium infection in Sanhuang chickensThe Sanhuang chickens was randomly divided into 4 groups,including blank group(NC),infection group(STM),control group(DC+STM)and test group(SA+STM),with 5 repetitions in each group and 10 chickens in each repetition.The test group and the control group were respectively added with the single-atom additives or trace element premixes to the basal feed,continuously.On the 8th and 9th days,Sanhuang chickens were infected with Salmonella typhimurium at a dose of 10~9CFU/mL by gavage,0.5 mL per animal,once a day.The results showed that theclinical feature of chicks in STM group included depression,dishevelled feathers,fond of lying and white loose stool,while clinical feature of chicks in SA+STM and DC+STM groups were found only depressed and lyingand no white loose stools.The average weight gain of STM was significantly lower than that of other groups(P<0.05).The amount of Salmonella typhimurium in cecum or liver and spleen in SA+STM and DC+STM groups were significantly lower than that in STM group(P<0.05).The spleen index in NC group was significantly lower than that in other groups(P<0.05).Comparing with NC group,the mRNA expression level of IL-6 in STM group increased significantly(P<0.05),CLDN in STM and DC+STM groups decreased significantly(P<0.05).There are a large number of gray-white lesions on the surface of the liver of chicks in the STM group,and the microscopic examination shows that the liver tissue structure is chaotic and full of inflammatory cells,while the liver lesions of the chicks in the SA+STM and DC+STM groups are mild.The VH of duodenal in the STM groups was significantly lower than other groups(P<0.05),while CD was significantly higher than other groups(P<0.05).Finally,16SrRNA high-throughput sequencing was used to analyze the fecal flora of chicks five days after infection.The results showed that single-atom additive and trace element premixed feed could adjust intestinal flora and resist the invasion of Salmonella typhimurium by reducing the relative abundance of Anaerotruncus and Escherichia Shigella and increasing the relative abundance of Lactobacillus.To sum up,the single-atom additive has good bacteriostatic effect in vitro,safe,non-toxic and non-irritant.The addition of 3g/kg feed can improve the growth performance of Sanhuang chicken,promote the development and improvement of intestinal tissue structure and gut microbiota,protect intestinal tissue and flora,improve the immune function of the body,and prevent the infection of Salmonella typhimurium.