Effects Of Immune Stress On Digestive System, Immune Function And Intestinal Microbial Flora In Broilers

It is apparent that many factors can influence the immune response of an animal understress. Stress can suppress, enhance or have no effect on the immune response of an animal.There are many interacting factors influencing the immunological response of an animalunder stress, some factors in the homeostasis of broilers directly or indirectly affect theirimmune status, and immunosuppression induced by stress is manifested by failures invaccination and increased morbidity and mortality of flocks. This article attempted to studythe effect on different immune stress in growth performance, digestive enzyme activities,nutrient transporters, immune function and intestinal microflora in broiler chickens, aiming toreveal the mechanism of immune stress' effects on nutrient utilization and to provide atheoretical basis for optimizing the broiler immune program.1. Effects of immune stress on performance parameters and digestive function in broilerchickensImmune stress is the loss of immune homeostasis by external forces. The purpose of thisexperiment was to investigate the effects of immune stress on the growth performance, smallintestinal enzymes and peristalsis rate, and mRNA expression of nutrient transporters inbroiler chickens. Five hundred and fourty1-day old broilers (Cobb500) were randomlyseparated into5groups with9replicates per group and12birds each replicate; Group1=novaccine (NV); Group2=simplified vaccination (SV); group3=conventional vaccine (CV);group4=lipopolysaccharide (LPS)+conventional vaccine (LPS); group5=cyclophosphamide (CYP)+conventional vaccine (CYP). The results demonstrated thatimmune stress by LPS and CYP reduced body weight gain (BWG), feed intake (FI). However,feed conversion ratio (FCR) remained unchanged during the feeding period. Relativeindicators were measured on d21and42. Duodenum and jejunum relative weight index ofLPS group is lower than other groups on d21(P <0.05); and there was no significantdifference of indicators between different groups on d42(P>0.05). LPS and CYP increased intestinal enzyme activity, relative expression of SGLT-1, CaBP-D28k and L-FABP mRNAs(P <0.05). Intestinal motility of LPS group and the CYP group were lower than the controlgroup and the conventional group (P <0.01), and there was no significant difference ofintestinal motility between different groups. LPS and CYP injection had a negative effect onthe growth performance of healthy broiler chicken. Immune stress demanded a higherconsumption of energy resulting in the reduction of the synthesis of inflammatory factors, FIand BWG, which finally inhibited the growth of broilers. The present study demonstrated thatNV and CV could improve growth performance while enzyme activity in small intestine andrelative expression of nutrient transporter mRNA of NV and CV were decreased under theconditions of a controlled rational feeding environment.2. Effects of immune stress on immune function in broiler chickensThis experiment was conducted to determine the effects of different immune statuses onimmune function of broiler chicken.1801-day AA broilers were allocated to four groups;each treatment had5replicate cages of9broilers per replicate pen. Different immune stressmodels, including the control group=no vaccines (NV), conventional vaccines group (CV),immune hyperthyroidism group (LPS) and immune suppression group (CYP) were conductedin this study. The T lymphocytes and subgroups were isolated from periphery blood fromimmunized and unvaccinated birds and were detected by CD3/CD4/CD8triple labelling andflow cytometric analysis and MTT assays, respectively. The results showed that, group LPSthymus index was higher than other treatment groups on day21and35(P <0.05); CYP grouphad reduced thymus index trend (P>0.05); LPS group increased significantly spleen index onday21and35(P <0.05), bursal index in CYP group was significantly lower than the othergroups on day21,28,35and42(P <0.05). Compared with NV group, sIgA level of LPSgroup and CYP group decreased (P <0.01); the serum IgG of42days LPS group increasedsignificantly (P <0.01) comparing to the NV and CV groups. With the increasing of day agebetween treated groups antibody titer appear increasing trend, CPY and LPS inhibited the T, Blymphocyte proliferation, and CD4+/CD8+T cell percentage of LPS group was significantlylower than NV group (P <0.05). LPS stress increased the cellular immune response ofchicken. Tolerance of chicken to CYP increased with age.3. Effects of immune stress on intestinal microflora and common bacteria changes ofbroiler chickens1801-day AA broilers were allocated to4groups; each treatment had5replicate cagesof9broilers per replicate pen. Different immune stress models, including the controlgroup=no vaccines (NV), conventional vaccines group (CV), immune hyperthyroidism group(LPS) and immune suppression group (CYP) were set in this study. On d21,28,35and42, each treatment group from each of6chickens, after slaughter, sterile operation collectedjejunum, ileum and duodenum and cecum intestinal contents. The results showed that theDNA fingerprinting of ERIC-PCR had high stability and repetition. Different immune statusaffected gut microflora to different degrees, and as age varied, the dominant microfloracorrespondingly changed. The diversity of cecal microflora was mostly obvious in LPS+general vaccination treatment and CYP+general vaccination treatment. In the present study,based on cluster analysis, the similarity of gut microflora in negative control was relativelystable; and among all treatments, the similarity of duodenal microflora was the highest at75%,followed by cecum (40%), jejunum (38%) and ileum (39%). These data suggest that immunestress can affect gut microflora in broilers. More specifically, changes happened in deodenumwere relatively stable, and for other tracts, compared with the CYP+vaccination treatment, theLPS+general vaccination treatment had more significant influence on microflora. Theapplication of RT-PCR on immunological stress test in the digestive tract of broilersEscherichia, Lactobacillus, Bifidobacterium and Enterococcus were analyzed. The dynamicdistribution and changes of the four bacterial species in the broiler's digestive tract were alsoanalyzed systematically. Among the4genera of bacteria, changes mainly concentrated in theileum and cecum, E. coli content:5.03-7.88; Lactobacillus content:5.48-10.34;Bifidobacterium content:4.11-7.98; Enterococcus content:5.61-8.79. The results showed thatimmune stress makes the four bacterial species in broiler's digestive tract changeconspicuously in their genic copy when comparing with CV. In which, the changes of the fourbacterial species mainly represent in ileum and cecum, while the changes of days byduodenum species is not clear.In summary, the reasonable control of broiler rearing environment, no immune orsimplified immunization led to the same production performance as conventional immunity.Immunological stress changes in the gut flora composition, reduces intestinal mucosalimmune function, subsequently affects the humoral and cellular immune responses. Themechanism of intestinal microflora change needs further research.