| Due to the prohibition of antibiotic growth promoters(AGPs),the healthy breeding of broiler is challenged.It is necessary to search for effective natural antibiotic alternatives.Xylo-oligosaccharides(XOS)is a kind of prebiotics which can be utilized by hindgut probiotics to produce short-chain fatty acids(SCFAs).Probiotics can inhibit the colonization of harmful bacteria in the intestinal tract,while SCFAs can provide energy sources for intestinal epithelial cells to promote intestinal development.Gamma-irradiated astragalus polysaccharides(IAPS)is a physical modification product of native astragalus polysaccharides(APS)irradiated by gamma rays.Previous study showed that gamma irradiation modification with a proper dose could decrease molecular weight of APS and enhance its immunomodulatory activity while retaining its molecular structure.Thus,we speculate that XOS and IAPS could work together in a synergetic manner to improve broiler performance by enhancing broiler immunity and improving intestinal health.Therefore,the aim of this study is to explore the effects of dietary XOS,IAPS,and their combination administration on growth performance,the body’s immunity and intestinal barrier function of broiler chickens.1.Effects of XOS and IAPS on growth performance,antioxidative ability and immune function of broilersA total of 240 one-day-old Ross 308 broilers were allocated into 5 groups for 21days: control(basal diet),CTC(basal diet supplemented with 50 mg/kg chlortetracycline),XOS(basal diet supplemented with 100 mg/kg XOS),IAPS(basal diet supplemented with 600 mg/kg IAPS),and XOS+IAPS(basal diet supplemented with 100 mg/kg XOS and 600 mg/kg IAPS).The results showed that:(1)As compared with the control group,dietary CTC administration could significantly increase the average daily gain(ADG),the thymus index,and the total antioxidant capacity(T-AOC)of broilers(P < 0.05).And birds in the CTC group had lower serum malondialdehyde(MDA)concentration than those in the control group(P < 0.05).(2)As compared with the control group,dietary XOS,IAPS,and XOS+IAPS administration could significantly increase thymus index and serum lysozyme activity(P < 0.05),and dietary IAPS,and XOS+IAPS administration could significantly increase inducible nitric oxide synthase(i NOS)activity and serum nitric oxide(NO)content(P < 0.05).In addition,birds in the XOS+IAPS group showed higher ADG and T-AOC,as well as lower feedto-weight ratio(F/G)and serum MDA concentration(P < 0.05).(3)As compared with the CTC group,dietary XOS,IAPS,and XOS+IAPS administration significantly increased serum lysozyme activity(P < 0.05).As the same time,birds in the IAPS and XOS+IAPS group showed higher i NOS activity and NO concentration than those in the CTC group(P < 0.05).In conclusion,dietary XOS,IAPS,and XOS+IAPS administration could improve the immunity of broiler,the effect of which was better than CTC.In addition,the combination of XOS and IAPS had a better potential as chlortetracycline substitute for improving the growth performance and the body’s antioxidant capacity.2.Effects of XOS and IAPS on intestinal morphology and intestinal barrier function of broilerThe experiment design is the same as experiment 1.The results showed:(1)As compared with the control group,dietary CTC administration could significantly increase the villus height(VH)and villus height to crypt depth ratio(VH/CD)of the 3segments of small intestines(P < 0.05),the number of goblet cells of ileum,the number of secretory immunoglobulin A(s Ig A)producing cells of duodenum and ileum,and the m RNA expression of claudin-1,claudin-3,ZO-1,occludin,interleukin-2(IL-2)and lipopolysaccharide induced TNF factor(LITAF)of jejunum.In addition,dietary CTC administration significantly reduced the plasma D-lactic acid concentration as compared with the control group(P < 0.05).(2)As compared with the control group,dietary XOS,IAPS and XOS+IASP administration significantly increased the VH and s Ig A producing cells of the 3 segments of small intestines,VH/CD and goblet cells of jejunum,and the m RNA expression of ZO-1,occludin and LITAF of jejunum(P < 0.05);In addition,as compared with the control group,dietary XOS+IAPS administration significantly increased the m RNA expression of claudin-1,claudin-3 and IL-2 of jejunum(P < 0.05),and the serum reduced D-lactic acid concentration(P < 0.05).Moreover,there was a significant synergistic effect between XOS and IAPS on increasing the number of duodenal goblet cells and jejunal s Ig A producing cells,and ileal VH and VH/CD(P < 0.05).(3)As compared with the CTC group,dietary XOS and IAPS administration significantly decreased the duodenal and jejunal VH/CD(P <0.05).In addition,birds in the XOS group had lower the m RNA expression of claudin-3 of the jejunum than those in the CTC group(P < 0.05).Birds in the IAPS group had lower the m RNA expression of occludin of the jejunum than those in the CTC group(P< 0.05).At the same time,birds in the XOS,IAPS,and XOS+IAPS groups had significantly higher the number of duodenal and ileal s Ig A producing cells than those in the CTC group(P < 0.05).In conclusion,although XOS and IAPS significantly promoted the development of the small intestinal and enhance the intestinal barrier function of the small intestine,the effects of XOS+IAPS was better than that of XOS and IAPS alone,equivalent to that of the CTC group.3.Effects of XOS and IAPS on cecal microflora and the concentration of shortchain fatty acid of broilersThe experiment design is the same as experiment 1.The results showed:(1)After filtering of raw tags and removing of chimeric tags,an average of 109316 effective tags per sample was obtained.The estimate of Good’s coverage reached greater than 99.42 %for all cecal samples.The Venn diagram showed a total of 580 OTU are shared among the 5 treatment groups.In addition,the unique OUT numbers corresponding to control,CTC,XOS,IAPS and XOS+IAPS were 133,143,127,103,and 125,respectively.(2)None of the dietary treatments had a significant effect on the Shannon and Simpson indices of the cecal bacterial community(P > 0.05).However,both dietary IAPS and XOS+IAPS supplementation significantly decreased Chao1 index as compared with the control and CTC groups(P < 0.05).(3)No distinguishable clustering of the samples was evident based on the dietary treatments.The results demonstrated that the cecal core set of microbiota of broilers had not been changed by dietary treatments.(4)At the phylum level,Firmicutes and Bacteroidetes were the most dominant phyla,followed by Proteobacteria,Epsilonbacteraeota and Cyanobacteria.Dietary XOS+IAPS administration significantly increased Firmicutes to Bacteroidetes ratio,increased the proportion of Ruminococcaceae,as well as decreased the proportion of Barnesiella and Negativibacillus(P < 0.05).However,dietary CTC administration significantly increased the proportion of Bacteroides,and decreased the proportion of Negativibacillus(P < 0.05).In conclusion,dietary CTC administration havs an impact on specific bacteria in the cecal chyme.Dietary XOS+IAPS administration,which can change the diversity of the cecal chyme,is more effective than CTC.Moreover,the microflora targeted by CTC and XOS+IAPS is different.In conclusion,dietary XOS and IAPS administration enhanced the immunity of broilers,and the effect of which was better than that of chlortetracycline;XOS and IAPS administration promoted the intestinal barrier function and the development of small intestine,but the effect of which was inferior to chlortetracycline.XOS and IAPS had a synergistic effect.As compared with XOS and IAPS,the combination of XOS and IAPS had a better potential as chlortetracycline substitute for promoting the growth performance,antioxidant capacity and intestinal barrier function of broilers.In addition,XOS+IAPS could increase the relative abundance of cecal beneficial bacteria and create a healthier cecal flora for broilers. |
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